I own these two wheels so I feel I am qualified to give my opinion. The GT3 RS V2 is a great feeling wheel. The thick, Alcantara wrapped steering wheel is hard to beat for me. I wasn't sure how I was going to like it at first, but I absolutely fell in love with it. I also love the fact that you can adjust wheel settings on the fly, from the wheel itself. That is brilliant, and I wish more manufacturers would implement that kind of system on their wheels.
Another thing that I feel is brilliant is the cable system. It is fully modular, and all of the cables (USB, Power, Pedals and Shifter) are FULLY detachable from the wheel. This may not sound like a huge deal if you have your wheel hard mounted or in a cockpit, but for someone like me who switches back and forth between driving and flight sims it's a godsend. It makes removing the wheel from my desk that much easier, just disconnect the cables from the wheel's base, and toss it it on my bed...
The FFB for me was a mixed bag. The feel of it was a lot smoother than my previous wheel (DFGT), and took some getting used to, but I ended up preferring it. I think this is because of the belt drive system. The FFB could be very strong, but with too much force dialed in, it felt like the belt would slip and get very jerky. This is something I could not get used to, and really hurt my lap times, so I ended up lowering the FFB to a point where I think I wasn't seeing any benefit in feel over my old DFGT. Kind of negated the point of buying a higher end wheel in the first place...
The T500 RS on the other hand is a completely different animal. It's a belt drive wheel as well, but definitely does not feel as soft, or 'dampened' as the Fanatec. I think this is due to the extreme power of the FFB motor. It's FFB is sharp like my old DFGT, but with a MUCH 'cleaner' and tighter feel. There is no rattling or gear lashing or anything like that, just tight, sharp, accurate and STRONG FFB. Between the GT3RS and the T500RS, as far as FFB is concerned, the T500 wins HANDS DOWN.
The wheel itself doesn't feel nearly as good to me however as the GT3 RS. I really got spoiled by the meaty, alcantara wrapped wheel. In comparison, the T500 wheel rim is skinny (to me), cold and hard. It also scratches easily, which I find weird. The unit itself is also MUCH bigger than the Fanatec. I'm forced to move my monitor back 8-10 inches from where I had it with the Fanatec just to make room.
Another gripe is the damn cabling. I was hoping Thrustmaster would take a page from FANATEC's book and have the cabling system fully modular, but it isn't. The USB cable is hard-wired into the base unit, making removal of the wheel from your desk a nightmare. Every time I want to clear my desk off, or switch to a Joystick I have to crawl under my desk, reach around the back of my PC to disconnect the usb cable, then fish it all the way back up to the top of my desk... Real pain-in-the-ass. It doesn't help that the wheel is HUGE and weighs like 10 lbs. In it's defense, I suppose this type of wheel was made for permanent mounting in a cockpit or something...
Overall, I prefer the T500 RS, and that is now my main wheel. I still have the GT3 RS as a backup, however.
I paid 179.99 for the GT3, and 200.00 for the Clubsport pedals, making the set come out to 379.99. You can save even more money by going with the standard pedals that only cost 49.99. That would bring the set to 239.99, which is a STEAL!
The T500 RS on the other hand, was 599.99 and this included (awesome) pedals. So these two wheels are obviously in two completely different price brackets.
My verdict; if you have the money and the desk space/real estate, DEFINITELY go with the T500RS, if not he GT3 is still a great wheel, with some definite advantages, for the price.
If you have any more specific questions, ask away!