I've got a Pro Circuit pipe on my bike. It makes the motor run great. From what I have read, the PC pipe makes more power (higher peak) than the FMF rev, but the FMF rev has more over-rev (broader power range). The seat of my pants tells me that the power increase from stock to the PC is HUGE. PC powerband on a 200 is as follows: relatively soft bottom, strong hit into killer mid range, screaming top. With the addition of a torque ring (1/8 or 3/16 inch, I think) it changes to: respectable bottom, smoother transition to killer midrange, screaming top.
If you're looking for power, you WILL NOT BE DISAPPOINTED with the Pro Circuit pipe. Compared to the FMF pipe, you may have to shift slightly more often to stay in the powerband of the PC pipe; however you have more power on tap. In my opinion, I can deal with shifting more if it means I have more power at my disposal.
As far as the gauge of metal...not a big deal to me. I have yet to dent my PC with no pipe guard. If you are likely to get in a crash that will result in pipe damage, your best bet in protection is a pipe guard; the gauge of metal will probably make little difference (try hitting each pipe hard with a sledge hammer, you'll see). Plus there's the issues with FMF vs. Pro Circuit fit that have been discussed lately...