Better is a very subjective word.
It's more fun, at least for me and everyone who tried it at my place. That's what convinced me to switch but I switched a long time ago.
Disadvantages? Not sure... here is what I think:
1. If the wheel is plugged in _and_ has batteries it sometimes pauses the game without you pressing the start button, mildly annoying in free run if you're on your fast lap but devastating if you're racing online.
Solution: remove the battery if the wheel is plugged in, no idea why it works but it seems to.
Caveat: this may have been fixed already with newer wheels, mine is old.
2. It's more physical, can be either an advantage or a disadvantage. It certainly makes the experience much more engaging, you'll find yourself leaning in your seat in the corners for no good reason. It also feels better and I personally think that learning to feel the car with the wheel helped my real life autocrossing.
On the other hand, it can be a con if you're feeling lazy and just want to bang away at buttons in your recliner. I just don't play Forza when I feel so.
3. It'll take you some time to get to the same level of skill you're at with a gamepad, but it goes both ways. It's just about what you've spent time getting used to. Unlearning your gamepad habits can be hard, but it's fun.
All that said, I've been playing Forza with the wheel exclusively for a year and half or so. Wouldn't do it any other way.
R.I.P. PaleRider

Personal opinions above are just that, personal.