Studio vs. Independent
On every cam site, you can sign up independently (where you work directly with the website) or you can sign up through a studio. All studios take a percentage of your pay, which varies from studio to studio.
Benefits of working independently
Biggest benefit: you keep the money you earn. The cam site will take its share of the money earned, and the rest is sent directly to you via the payment option you choose. You don't have any quotas to hit, no hourly requirement, no schedule. You are your own boss, essentially.
Cons of working independently
If you are not savvy with technology or with how to get around the Internet, you may need someone to help set things up for you. You may need some guidance on how to get started, or someone to go to with questions about your taxes. Studios *might* provide this for you (depending on the studio. Some are completely useless and just take your money.)
With a little bit of research, you can become a successful cam girl without a studio. Sites like this wiki are out there to help girls make the most money from being a cam girl without having to depend on a studio.
Benefits of working with a studio
A useful studio will take care of some of the more technical and financial things for you, so that you can focus on your cam time. They may promote and advertise you and drive traffic to your room while you're on cam. They may provide you with hardware or software, may even provide you a physical studio to work in, so that you don't have to set up a cam room in your home. They receive payment from the cam site, take their cut, then send you a check for the remainder. A useful studio can make things simple for you, and may be worth the cut of your earned income that they take if you need the help.
Cons of working with a studio
Biggest con of a studio is that you don't keep all of the money you earn. They also may require you to work a certain schedule, a minimum amount of hours each day/week/month, may have a minimum amount of money they require you to make each day/week/month. They may have it written into their contract that you cannot work with certain sites, or that you cannot work independently for a set amount of time after leaving their studio.
There are many "studios" that hide the fact that they are a studio. They make their website look identical to a cam site that you're signing up to, or make their company sound like they're an actual cam site, but in fact they will just sit back and take a cut of your income without providing any sort of help to you.