I own an older Exmark Ultracut series 4 -60" deck Laser. Having demo'd both the Exmark & Scag (after my purchase) at the GIE, I have a real high respect for Scag.
The most noticeable thing for me between the two, was the tight ass/low input controls of the Scag. There's a totally different feel between the two machines. The Scag has a unique feel of it's own.
Exmarks pumps/controls feel similar to Ferris, Toro, JD, Great Dane and some others. Whereas, Hustler might be on the other end with very well damped controls which are very easy to get used to.