G27 still rules!!
go for it
...speaking about simracing in general, i would agree totally. I had the G27 before and it was nice, better to say more than enough for every single sim.
Then came rFactor2, and it was little different.
Suddenly i was able to feel so much more details through the wheel, as i never felt before with sims like rFactor1 (leo & realfeel), Race07, even nkPro and iRacing dont offer that much details through the wheel.
So as i have all these superb FFB-Details in rF2 on one side, there was this annoying rattle of the Logitech's on the other side, so i decided to go the belt-driven-way...
I bought the THRUSTMASTER T500RS one week ago.
Simply amazing how this wheel lets you feel all the different details like accelerating, braking, slipping, sliding, curbing, off-roading, bumping... and it is faster than light

and still smooth and direct... just get off the wheel if your back end slips and it will countersteer automatically very quick, just need to do some little corrections, catch the slide and throttle straight away... really that much fun !
So conclusion:
If youre not going to lock tyres under braking in iRacing's Mazda or simply not driving rF2 (the sim with the best FFB so far) then go for the G25/G27, 'cause its more than enough for all those poor-FFB-titles (compared to rF2).
If you want to drive rF2, what is the reason you're here for i guess, you should definately go for a belt-driven-wheel like the TM T500RS, which is actually the cheapest/best wheel available (got mine for €400 on amazon including pedals i dont use). Add some ClubSport-Pedals and youre good for the best experience in simracing so far.
PS: i doubt that spending more money on CSR-E or even CSW will add that much more of immersion, details or smoothness. So T500RS and rF2 is the ultimate combination here !