I started on brewers best kits. They were my gateway drug into home brewing, so to speak. They were okay as far as beginner kits go. They made decent enough beer, but the instructions included were a little questionable.
Personally, I think you would be better off using extract ingredient kits from some of the major online suppliers such as Austin Homebrew, Northern Brewer, or Midwest Supplies. The ingredients are generally fresher, and the instructions are better. There's no telling how long those brewers best kits sit in their boxes before you open them.
That said, if someone offered me one for free, I'd take it in a heartbeat. That's coming from an all-grain brewer. Free beer is free beer.
Edit: I've never used a Coopers kit, so I can't give you a basis for comparison.
I had someone offer me the brewers best kit for 40 bucks. Comes with fermenting and bottling bucket. Or I could go with the cooper's, which just comes with their new fermenting bucket with the krausen collar.
I'm new to this stuff, I was just hoping someone on here has maybe used both and could guide me one way or the other.