First of all, you should not set the FF in the Logitech Profiler to 150%, because it will severely exaggerate the small forces (for example, wheel heavily jittering due to engine vibration). I'd recommend 105%, which is a nice compromise between keeping the forces such as LFS intended and removing the weak/dead zone in the middle of the G25's rotation. You might want to try a bit higher values to feel small bumps better, but at 150% I can guarantee you that you'll start experiencing mystery forces that shouldn't be there.
Second, setting the FF high in LFS might be more realistic in terms of feeling small bumps (off road driving is really fun then), but overall it will just lower the dynamic range of felt FF forces, because any normal steering forces will immediately max out on the wheel. You'll also have to grip the wheel really hard to prevent oscillation. Personally I use 105%/40%, but each to his own, I guess.