It's pretty much like anything else. You will find plenty of people on either side of the fence on any product. I've owned all three (G25 -> Fanatec Turbo S -> G27) I was originally a G25 owner (loved the wheel, but had to mod my shifter because it was just too weak) and I made the move to the Fanatec Turbo S + Clubsport pedals because I wanted a multi-platform wheel.
The size of the wheel is very nice and it does have both and h-pattern and sequential shifter (in addition to the paddles on the wheel) although, you need to change them as it's not like the G25 where the same shifter can be setup in either mode. Lots of buttons on the Fanatec, which is also nice.
The Clubsport pedals, when they worked, were definitely a couple of levels above the G25, but the wheel just never felt right to me and the pedals (both throttle and brake) had issues with less than 2 months of use. I was not a first batch buyer, so the pedals had already gone through some improvements by the time I got mine. After getting no real support on them, I boxed them up and went and bought the G27 and never looked back.
The G27 is pretty close to the G25, but the wheel is a bit more smooth and has a few more buttons. Unlike the G25, the G27 shifter only has H-pattern, no sequential so you would want to consider that. The G27 pedals are a bit better than the G25 (better out of the box setup for heel-toe), but certainly not an evolution. As I said, you will find plenty of people with pros / cons of any product, but make sure you consider the support aspect of your purchase as well.
Good luck with your choice and may which ever way you go, be problem free :smile: