Lighting Studio lights?

Do you mean the pros and cons of using studio lights versus on-camera flash? No contest. Studio lights win out every time. The greatest advantage of studio lights versus on-camera flash is that they can be positioned anywhere you like. As the pattern of light and shadow is how we convey the three dimensions of an object in a photograph's two dimensional space, this is pretty important. Have a look at my thread on studio lighting styles to show you what difference the position of the light can make. http://www.denofangels.com/forums/showthread.php/621625-Mau-s-Photography-Tutorials-VI-Studio-Portrait-Lighting-Styles

Another advantage is that you can buy or make modifiers for studio lights that you can't as easily with on-camera flash. So, this would be equipment to diffuse the light and soften shadow edges or equipment to focus the light and deepen the shadows.

If you are using off-camera flash with suitable modifiers, the advantages of studio lights disappear. In fact, because of the sheer power of flash, it is taking over from studio lights for many (most?) serious photographers.

 

Good old fashion light boxes are really good at providing diffused light; you can pick them up pretty cheap on eBay and amazon.

 

Lots of options for lights. If you are starting out and experimenting, desk lamps with homemade modifiers can work fine. However, because they only give out very little light, you have to use a tripod or similar support and risk having noisy (grainy) photos, because of the long exposure or high ISO needed. I personally use cheapo light stands and softboxes off eBay. The softboxes are pretty shoddy and my small (30cm) ones won't take halogen light for more than a few seconds before smelling of melting plastic. But I would still recommend softboxes over light tents for versatility. A light tent is good if you want that high key, lit-all-over-with-few-shadows effect, but less useful if you want moody, dark shadows, as you can not focus the light.

So, from having tried many combinations over the years, I now use large (60-40cm) softboxes for large subjects and small (30-30cm) softboxes for small ones. I can then mask off bits of it with black paper if I want a more focused light. I also have made internal baffles for them (which is a square of white cotton that you string up inside the softbox to shield the direct light and avoid hot spots of light, which are very annoying on shiny resin). I use domestic, halogen bulbs, as these give the best range of colours (colour rendering), although they get hot VERY quickly. I use a splitter, which is a device that lets you screw two light bulbs into one socket and so double your light output (and heat).

Don't forget to set the white balance on your camera for whatever bulb you are using. When I started out, I listened to those people who recommended CFL swirly bulbs, as they could be got in "daylight" colours. However, they are expensive, they break just by looking at them and they make skin tones look like zombie flesh. Also, there is no one colour of daylight and they always looked too blue if I set my camera to its daylight white balance setting. So, always best to set the white balance for each bulb you use and to choose your bulb on the basis of other criteria.

 

Some clarification is needed here too about what the OP considers "studio lights". At the broadest level, studio lighting falls into two categories: flashes (xenon strobes) and always-on "hot lights". Hot lights are so called because historically they were tungsten/halogen lights that get extremely hot, but now this term refers to any light that is continuously on, even if it's a relatively cool fluorescent or LED light source.

Hot lights have a very obvious advantage for someone just getting into lighting: you get immediate feedback as you move the lights around, rather than having to take a photo, adjust, and repeat as you do with strobes. Dedicated studio strobes usually have hot lights built into them, called "modeling lights" that serve to give you this preview while positioning them, but it's not exactly WYSIWYG like with hot lights. Most people just getting into lighting with flash will want to purchase battery-operated hot-shoe flash units, since they have the flexibility of being able to be used anywhere, whereas studio strobes are not portable in the walkaround-with-them sense. With these flashes, you don't have modeling lights, so you have to either make your own (clip a CFL beside the flash, for example) or deal with trial and error.

For hobby doll photography, you won't need studio strobes, ever. Even if you're really into camera gear, your money would be better spent elsewhere. Higher-end hot-shoe flashes ('speedlites') can do everything you would ever ask of studio strobes, the power output of studio units** is just not needed for doll-scale stuff. Speedlites can work with light modifiers like softboxes, beauty dishes, umbrellas, etc., just like studio units. They have the advantage of being much more generally useful too; I use speedlites in most of my outdoor doll photography, both on camera and off, especially for fill-flash in bright sunlight. If you go this route, be sure to get units that can do high-speed sync with your camera model, so that in the sun you are not limited by prohibitively slow shutter speeds (most cameras can only sync up to 1/180 or 1/250 without high-speed sync compatibility with the camera body). I could give you the quick pros and cons of certain models if you could share more information about what camera you use and what types of situations you intend to shoot in.

**Some studio strobes actually can't be dialed down low enough in output to easily work with dolls, without requiring them to be far away or reduced by screens or bouncing them. These lights are made for big power output in big studio spaces.

 

Both of your cameras have Canon's "integrated optical speedlite transmitter" feature, which allows the camera to control multiple off-camera speedlites that have no wired connection to the camera, through pulses sent using the built-in pop-up flash on the camera body. This means you don't need one of the high end speedlites (500 or 600 series) or dedicated hot-shoe controllers in order to use wireless slave flashes. The built-in pop-up flashes on these cameras can be set to only control the external flashes, and not contribute it's own light. So the most basic system would be to get two E-TTL compatible flashes, and set them up as key and fill light slaves. I know the 7D2 has the very latest in in-camera speedlite menu options for setting the channels and groups, relative output strengths of the slaves, etc. Not sure what the T5i offers, but probably not too different.

Canon's speedlites starting with the 270ex and better can all be optical wireless slaves. Starting with the 430 models, you can also set flash output strength manually on the unit, rather than just as relative strengths through the controlling camera's menu system (or through a 500 or 600 series master flash unit's settings). There are a lot of ways to set things up, and it will probably take a bit of Googling and some Youtube tutorials to get an idea of the options. This page has some decent starter info too: http://pixsylated.com/blog/canon-speedlite-optical-wireless-fundamentals/

The system that works best for your cameras will not work for anyone who doesn't also have a Canon E-TTL master: either a T3i or newer, 60D, 70D, 7D, 7D2, etc. or a 550, 580, or 600ex speedlite. Also, while not advertised widely, newer Canon bodies like the 5D mkII, 6D, etc. which do not have a built-in popup flash can actually use the 90ex ($50) speedlite as a master! This little unit was made for the EOS M mirrorless camera, but I use it on my 6D in exactly this way, to control an external 320ex and 430ex II pair. If you're trying to set up a system anyone can use, regardless of their brand of camera, then things get expensive quickly, because the only way to do it is with a 3rd party radio control system (e.g. Pocket Wizard). Generic optical systems are can be a nightmare, because they trigger off any flash (horrible when you have people taking pictures of you taking pictures...), and are confused by things like red-eye reduction pre-flashes, strobing AF assist, etc. Radio wireless is the only way to go and even that will require that the cameras at least have a hot-shoe. The other option is a second hot light setup, possibly mounted on the same stands as flashes, so that the hot lights can double as modeling lights for positioning the flashes. You could put them all on one power strip to turn them off when using the flash setup.

Also worth noting, as I write this the Canon 430ex II is only $200. 2 days ago, canon announced the 430ex III, which has driven the current unit down to clearance prices everywhere. And I got my 320ex as a Canon refurbished unit for $109. You can get enough light for any BJD mini-studio on a very reasonable budget without having to even worry about dealing with off-brand equipment. And if you don't mind dealing with some possible quality control issues, or documentation entirely in Chinese, a company called Yongnuo makes knock-offs of the Canon 500 and 600 series units that are a fraction of the cost of the real thing, and overall get pretty decent reviews from enthusiast users. There are some reports of these units overheating in high-usage scenarios like wedding shooters, but they are $150 copies of $500 flashes...