Hustler Super Z hands down. Speed, cut, hill-handling, support, it is same league like Toro/eXmark, Kubota and Scag.
Gravely is good but not good enough to win or even gain market except their funky 34z. I have never seen Gravely mower handling big acreage accounts in my areas, it takes all day to do the areas, those huge accounts are cut by Super Z and Kubota ZD, it must have reasons.