I have both the Marc Anthony and the Bush-in-a-Bag. I much prefer the Marc Anthony as it is really a pants and jacket while the Bush in a bag is more of a poncho style. IMO there is less potential for your string to snag on the MA. Also, if you want to still hunt with your ghillie on the MA works fine but it would be real tough with the Bush in a bag. I haven't had my bush in bag on since I got the Marc Anthony. I can't envision a scenerio where the Bush in a Bag would be a better option than the MA.
All that said, they both conceal you quite well and I've had deer and turkeys very close while wearing either one.