Keylight is free and very capable. I prefer Primatte but its costs $500.
I suggest you find some tutorials and try them both out. You then can judege for yourself
There is a free trial for Primatte here. http://www.redgiantsoftware.com/products/all/primatte-keyer/
Both require skill and tweaking to go a good job. A great job requires footage with a high data rate and good lighting. A top of the line job requires excellence in every area of the production from costuming, makeup, hair, lighting and camera work. Either of these plug-ins, given a bit of tweaking and some garbage matting can do a passable job with poor quality footage, but really awful footage is pretty much a wash out.
keylight is not free unfortunately U_U
look you have to buy it
Not much better. Probably not better at all -- you have the most up-to-date keylight plugin available for After Effects, according to the Foundry web site. I wouldn't worry about it.
Instead, you should worry about getting the user guide and the training resources at the Foundry web site, and looking over the Keylight tutorials you'll find here on the Adobe web site and at the Creative COW.
Don't trust a tutorial made by some high school kid on youtube. Would you trust a high school kid to build a car for you?
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