This is simple, I can buy Parallels for $80 and get lesser performance or Windows 7 for $60 and get the best possible game experience over a spectrum of games on my 2011 MBP (see signature). Dealing with windows does require more effort but I'm willing to put out the effort for a better frame rate or possibly still play a game, that parallels can't handle.
I recently settled into Parallels because of all the aggravation I was getting with windows under Bootcamp. Before I settled into parallels I did set up windows under bootcamp again but found that windows ran really sluggish with trails all the screen when I dragged a window etc, this does not happen in parallels and it did not happen the first time I set up Bootcamp.
I'm happy, mainly because I prefer playing the older type games anyway. What does not run well enough under Parallels or a wrapper, Wine/Crossover nor has a Mac dedicated version I can live without. A bit of online investigation and a visit to The Porting Team site etc soon tells me whats going work and what is not.