I agree with wowbaggerBR. The T300 completely changed how driving games feel for me (or it could just be PCARS). The smoothness just makes it feel so much more real. I've used the G27 for like 5 years, and it's never felt this good. Although I can't try the G27 on PCARS (PS4), I don't think it could come close to the T300 in terms of feel. Before I got the T300 I was pretty convinced that it couldn't be that much better than the G27, but it is. If I could still use the G27, I'd probably think it was fine, and I'd still enjoy the game, but it wouldn't be the same level of immersion. The T300 being belt driven really feels like you can feel the tires scrubbing on the track surface; it is most pronounced when driving the karts.
But then again, other than the wheel base itself, everything else about the T300 is inferior to the G27. The wheel is rubbery plastic instead of leather, the pedals aren't quite as good (but not as bad as everyone makes them out to be), and it doesn't come with a shifter. All of those could be rectified, but I'd have to spend another ~$500 on top of an already ~$500 wheel, whereas the G27 cost ~$300 in total. Reliability on the T300 is also suspect although I personally haven't had any issues yet (I've only had it for like a week). The G27 is pretty bulletproof; I've never had any issues with mine whatsoever over the years.