Big schools aren't all bad, however...
Big schools aren't all bad. First off, if you teach at a big school your more likely to get multi-engine time. While MEIs at smaller FBOs do get multi-engine time, it can be pretty sparse. Also, the instructor pay is higher then your average FBO at one of the big schools listed above. Finally, one more advantage of the bigger schools, especially those run by Comair and Mesa is that you've already got your foot in the door, so to speak.
When you look at cost, make sure to look at the whole picture. You need to figure out how much your going to lose by not working, how much living expenses are going to be, how much the training is going to cost, and finally how much you will make as an instructor. For example, let's look at the cost of a school like PanAm. Let's also assume you make approx. $30,000/yr now, and your living expenses are $1000/mo. Your cost of training, including the opportunity cost will be this. Training is about 8 months, $8000 to live, approx. $50,000 for the training, total cost is now $58,000. If instructors make about $25,000/yr gross, figure $20,000/yr net. After two years instructing you will have made back $16000, ($40,000 net income – $24,000 living expenses), for a cost of $42,000.
Here's another one, ATPs. Private takes three months, you do that at home. Making 30k a year again, you'll net $6000, minus $3000 living expenses, minus $4000 for your private, making the cost of your private $1000. If you then finish at ATPs, the cost will be $30,000 for training plus $600 for three months of living expenses (housing paid), for $30,600. If their instructors make about $18,000/yr gross, $15,000/net, and it again costs you $1000/mo to live, then your cost after two years will be $25,600 ($31,600 training cost - $6000 extra income).
Hopefully you can see where I am going here, don't just look at the training cost, look at the whole picture. Most of the numbers above are guesses, you'll need to look at your own situation and get realistic numbers from the school you're going to attend. (Hint: ask the students and instructors about costs and pay, the admission counselors will say most anything) If you make good money at your job now, I think you'll find your best option from a financial perspective is to keep your job and train at local FBO. I did train at a local FBO, but I quit my job half way through, and I'm wishing I'd kept it until I got my CFI. Also, plan for the worst case scenario, instructing for two to three years. If you can't survive on low wages indefinitely, then at some point you may be forced to quit aviation.
Finally, I'll throw my comments on uniforms. If you've read my previous posts on the topic, you'll see that I do not like schools that make you wear uniforms during your primary training. First off, some schools are charging students a couple hundred dollars or more for uniforms, and every dollar spend on uniforms is one less that can be spent on training. Also, since the cost of uniforms usually comes right out of your loan, the total cost of the uniforms will increase two to three times with interest, pushing the additional cost to over $1000 in some cases. Moreover, uniforms don't do anything to improve the quality of training, or increase professionalism. Like FlyinBrian said, even airline pilots don't wear uniforms during training, only when they will be seen by the flying public. Slacks and the polo shirt is a perfectly acceptable uniform.
What you have to do is take a look at the whole package. Costs, location, equipment, and time. Don't believe every line the schools will feed you, make sure to do some outside research. I hope you've found the above useful.
Send me a private if I can help some more.
) and a small outfit that primarily trained pilots for types and the United checkride but had a Middle East primary contract. Thus, I feel I've experienced a representative cross-section of flight training. 
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