While the choice is entirely yours but now that GT5 supports multi-screen setup, instead of coughing the money on a single 3D screen, you should seriously consider the multiple monitor setup. Here's a good example why (photo courtesy of Mr Latte):
I don't know how comparable it is to get one 3D screen versus three PS3 (or two if you've already got a PS3) and three smaller monitors (24" seems to be the ideal size). Although I have nothing against 3D but if you're more of a sim driving enthusiast and less of a movie/home theater buff, I would consider the other option.
You can find GT5 multi-screen setup guide here:
https://www.gtplanet.net/forum/showthread.php?t=189301
FC for all its worth was a decent game with a passable physics and FFB. One of the most fundamental property to a good FFB is that it should represent the feel of the front wheel in relation to the pavement. Yes, FC unlike GT5 does provide that understeer effect but that's about it. The best example of FFB in a driving/racing sim is obviously in iRacing and possibly netKar Pro. To describe the FFB in those two sims I have to quote the word of AeroMechanical from the NoGrip Racing forum:
"....iRacing feels a little more 'rubbery' if that makes sense. Pneumatic trail or whatever. There is a certain amount of springy play in the steering wheel around the area where the tire wants to follow its self aligning force.
It gives the impression better that what I'm doing is applying force to the wheel rather than simply turning it. It really is just an impression thing though."
In regards to the bolded statement- in FC it's the complete opposite. Other than the strong centre spring, you don't get the impression that you're fighting against the tires propensity to self-align. Basically it's the reason why most people find the driving to be challenging because almost every car in FC has a very strong oversteering tendency. Although I like the game (especially the moving clouds) and for the almost two years I played FC, I've regard it to be a decent game but overrated by some.
GT5, got almost everything right with its FFB implementation. Yes, it's not perfect but with my G25 cranked up to 10, cars like the Corvette Z06 feels absolutely sublime. And there's the track. Try comparing the Monza in FC and the one in GT5. In FC, the Parabolica feels absolutely tame (other than the oversteer issue). Whereas in GT5, the lateral pull one would experience in a long, sweeping like the Curva Parabolica is well presented in the FFB.