on the compare on the fanatec site the seem the same featurewise except for the Xbox 360 compatibility.
If they are the GT3RS seems a better deal for me!
another difference: according to Greekbull (see his mini review thread) it has same hard mounting points as Logitech wheels. not a deal breaker, but a nice touch since many rigs only pre drill for logitech. so in the end just makes it easier to hard mount 👍