Apparently, they both use the same engine; the 2610 may or may not have other tweaks, but the it's "set" to be able to run at a slightly higher RPM to gain that extra hp. Rated PTO speeds (540/2000) are set at the higher RPM level.
Thing is, many of us who have GCs find that they'll do a more than adequate job at less than "full, rated hp/RPM." And use less fuel as a result. That's one of the biggest reasons I got the GC over the Kubota- they generally have to run at a higher RPM, as I understand it.
I'll sometimes run the MMM at 2000 RPM, but usually lower; only use 2000 with the snowblower if the snow's wet & deep; otherwise 1500-1800 is plenty. Backhoe/FEL work rarely takes more than a fast idle, unless I'm trying to pull a stump or lift something that's quite heavy.
You'll see when you visit my pal in Leeds--see PM.