I have a DC SE LT2700-60D which I'll be going into my 4th season with. I absolutely love this machine. I'm not a commercial cutter, just a homeowner with about 3 acres and frequently, not a lot of time to get the yard mowed. The SE is very responsive, and fast enough for my use. I can easily mow at top speed and still leave a manicured cut. The ride is as good, if not better, than the Ransomes 3-wheeler it replaced, despite that the Ransomes' top speed was only about 6mph. I'd also borrowed my BIL's Scag TT a couple times (maybe about 2 hours seat time) and I think my DC rides a little better.
The Generac engine, for me, has been the most impressive engine I've had on a mower, and I've had Onan, Kohler, Briggs, & Kawasaki. The power and torque is more than enough to run doubles without any ground or blade tip speed loss except in really tall grass. I can't comment about fuel consumption for as I said, I'm just a homeowner so that's of low concern.
I'm sure the Grasshopper is a probably a nice machine, but you just can't ignore the extra ponies that the DC has to offer for the same price.