I have smaller tractors (24hp and 30hp) and don't have Power Beyond on either so I'll toss that question to someone else.
As for Question (1) a gear transmission is slighly more efficient than a hydro because of the design efficiencies of mechanical connections versus fluid power. Regarding HD work, I'm not so sure that is accurate, as commercial loaders are almost always hydro transmissions, but there are tasks that are better suited to gears and others that are better suited to hydro. Mowing the lawn is easier/faster with a hydro, especially if you have to maneuver the tractor around trees, landscaping, corners, buildings, etc. I wouldn't consider "tilling" with a tiller to be a "gear" job, but tilling with a plow is definately better done with a gear tractor. So is box blading. Front end loader work is more efficient with a hydro.
(2) how difficult is it to operate a gear tractor? Heck, even I can do that and I sell candy to kids and tobacco to people addicted to nicotine, so it can't be too tough to operate a gear machine if I can! I simply prefer hydro for use around my property. But anything I do with a hydro I could do with a gear, but it would take me longer. Then again, I don't pull a plow in the field.
Selective Control Valves are not needed for the implements you are talking about. A tiller will operate off of the PTO and is hooked up to the 3pt hitch. The front end loader will have its own valving and plumbing for its hydraulics. The bush hog will operate off the PTO and is connected to the 3pt hitch. The blade (grader or box) simply hook up the the 3pt hitch and are not powered in any way. A snow blower will be powered by the PTO, and hooked up to the 3pt hitch. It is possible that the chute rotation control is going to be hydraulically controlled (that is an optional feature) it would require a selective control valve (2 hose outlets) at the rear of the machine, that is the normal place to install them. 1 control valve has 2 quick connect hose outlets.
Steve, by the way, please fill in part of your profile. How big is your property, how much mowing will you be doing, how much tilling, how long of a drive do you have to maintain, etc. It will help others who are trying to help you if we know some basics about your potential needs.