I would absolutely recommend going with a Zero Turn.  The speed, comfort, and maneuverability difference is night and day.  I definitely agree with your initial choices of Gravely XL or the Raptor XD.  Another you could consider is the Bad Boy ZT Elite, which offers commercial-tier components at a similar price point.
One of my hard lines for buying my recent ZTR was a serviceable transmission, which is only available with the ZT-2800 or higher.  Most residential ZTRs use the "maintenance-free" ZT-2200 or equivalent.  Unfortunately for my wallet, this meant looking at the higher end residential mowers such as a Toro Titan, Gravely XL, Raptor XD, Bad Boy ZT Elite, etc.  Definitely worth it for the improved performance and longevity, though.  Just one replacement ZT-2200 transmission would knock out any initial savings from buying one of the lower end residential mowers, and the rest of the mower is better too.