when the porsche wheel is working properly, it is definitely better than the G25. you can find comparisons all over the place. smoother, stronger, more realistic force feedback, bigger wheel, and the Clubsport pedals are very nice. comes w/ paddles, gated shifter, and sequential shifter.
I've just got the normal 911 turbo, and the drivers for that are still buggy. sometimes they dont load settings and i have to do a few extra steps to refresh them. You'll see mixed reviews because early batches had some problems. Fanatec claims to have sorted all of that out for the new batches of wheels... too bad for me i had one of the earlier wheels, but I don't really regret the purchase.
racing single seaters feels a bit funny because of the wheel size. but you'll get used to it.