The Mark Todd ones are really durable and tough if you have a bit of a minxy horse that might trash it. I brought mine second hand off a friend as I was worried that Whisper would shred it within seconds but it's lasted really well and he's happier now he's not bothered by the flys. Don't know how much they are new though -probably pricey!
The 16hh-17hh horses down my yard all wear the same rug so must be quite popular.
I ordered a Premier Equine about 3 yrs ago and its still going strong and never moves. They have gone up a lot in price lately though. Im toying with getting a Rambo Protector as I really fancy one.
I have just bought a Premier Equine Bug Buster for my boy who is 17 h and very chunky. The rug is quite deep and fits him really well. I ordered a 7' 3''and it came with a free fly mask. In the current hot weather he does seem to stay cool which I did worry about. There is no back seam to rub his withers and a really long tail flap. I was most impressed by the delivery service too, I ordered the rug online at 4pm and it arrived the next morning. Cost about £62, postage about £4.