I have a Rogue. The suspension is definitely useful. I've mowed for ages on a Deere garden tractor (formerly a 345, in recent years a x758) and the Rogue is notably smoother. I can't compare it to any other zero-turn though. My 7 acres that I mow has a fair amount of roughness to it and the difference is noticeable. However, with a suspension comes trade-offs such as the deck 'digging in' (semi-scalping) in places where you go over bumps and the suspension flexes.
As suggested above, see if you can demo the models you're considering. Some dealers will even let you bring them home and try on your own property.
Rob