I'm sure, just by what you've said here, that you've got considerably more experience in the audiophile realm... but I love them.
I've used a fairly large number of "mainstream" gaming headsets before finally deciding to get something legitimate. Everything from a Logitech G330 up through the...
Yup
I paid $900 OTD. Not quite as bad. ;)
Still, for the amount of time you spend in a chair...I find it to be a worthwhile investment at either price.
My current 1440p Ultrawide setup:
PCHound Spec List: https://pchound.com/JXAyMH/
Full album of pictures here: http://imgur.com/a/Xzfom#0
Intel Core i7 4790K @ 4600MHz
EVGA GeForce GTX 780Ti Classified "K|NGP|N" Edition
ASUS Maximus VII Hero Motherboard
16GB Corsair Dominator DDR3 2133MHz...
I own both, and Col. Sanders nailed it. They're both great, but I think ProjectCARS is the better choice for Gran Turismo veteran.
But if you truly enjoy racing sims, buy both (eventually).