I have a Momo Racing, Microsoft Sidewinder (which is surprisingly good, I prefer it to the momo) and a G25.
The G25 isn't just some luxury product which is expensive because of lack of competitors. It really is as much better as the price suggests, if not more. Since I compared the Momo and G25 side by side, I have a good idea of their differences:
1. The pedals. The Momo pedals feel like soft plastic toys, and there's only two of them, with almost no resistance and feel unstable. The G25 are completely different; they feel just like a real car. Solid, long travel, much harder resistance, and different resistance for each pedal, heavy pedal box that stays put on the floor, even on carpet, pedals made of metal etc. Only the brake pedal lacks a bit of that hydrualic resistance. And there's a clutch pedal with the G25 which makes a big difference in realism and immersion, especially for some cars.
2. Shifter.
The Momo has a loudly clicking sequential shifter that can be moved on the steering wheel from left to right side. It's ok, but better have sealed headphones to avoid the click sound ruining the immersion.
The G25 shifter can be made sequential (where it is very quiet) or a not-as-loud-as-Momo H-pattern shifter, which works well, but is a bit light compared to a real shifter and care should be taken. It's very fun to drive certain cars with the H-pattern shifter. If you don't do any H-pattern shifting but only use pedals or sequential, the G25 has no real advantage here.
3. The wheel.
The Momo wheel has very limited rotation, even less than F1 cars. The momo has very strong force feedback, but the feel and reaction time is dreadful. For example, if the wheel is supposed to go 'light' in the game for any reason (losing traction in GT Legends, driving over a crest or oversteering much), it's barely noticable in the Momo - there is still so much sluggish resistance in the wheel that you have to overcome to move it, even without any forces acting on it from inside the game. This really makes it much harder to drive in some situations than it should be. It has the feeling of driving a car with a horrible electric powersteering filter that is malfunctioning or something..
The G25 has 2.5 turns of rotation (in contrast to the 0.5 turns of the Momo) and feels much more responsive. It's also quieter. When there are no steering forces (going 'light' again), it really is very light, and this adds a lot to feeling and makes it easier to drive, in accordance with realism. The lock-to-lock can be set inside the control panel to be less than 2.5 turns, to suit realistically different types of cars.
For anyone with simracing as a hobby, and who can afford the G25 without giving up too many other things, I can't recommend it enough. However, if you never use H-pattern shifting, you don't care about clutch and don't race much (or race anything less than the more hardcore sims out there), don't bother with a G25. It's features would be mostly wasted.