I had a Ferris IS1500 (I think that was the model) and I thought it was a really great mower. Most of the commercial mid mount mowers seem to be built tough. They are actually built tougher than I am because they absolutely beat the living snot out of me because when I mow, I mow fast so I can get it done. The Ferris definitely rode better than any other of the mid mount mowers I've had or used. My issue was that mid mount mowers leave larger areas uncut on inside corners, can't get under pine trees or reach out over the edge of my lake to keep me from having to use a weedeater any. After I put the Ferris in the lake for the 3rd time I realized that it just wouldn't work for me.
No mid mount mower rides as well as front mount mowers. Even without suspension, my front mount Grasshoppers ride better than the Ferris. However, you cannot get as many front mount mowers on a trailer as you can mid mount mowers and front mount mowers cost more since you literally have a self contained machine with a detachable mower deck out front. If I was to ever buy another mid mount mower, it would be a Ferris.
On a side note, I had two mowers that were identical except one was diesel and the other was gas powered. Both had 3 cylinder Kubota engines but one was gas and the other was diesel. Each machine had the same sized decks and within 1 hp of each other. I could mow the 10 acres around my house twice and have a little bit of fuel left in the 8 gallon tank with the diesel. I'd run out of fuel with the gas powered unit before I could finish mowing once with the same sized 8 gallon tank. So, based on my experience, the diesel mower gets just over twice the economy as a similar power gasoline engine.