I can pull a bit apart here as to some of the comparisons and being able to speak of three brands of zero turns that we sell my answers are from the shop.
The hydraulic
PTO is used on large farm tractors and is a easy engage compared to an electric clutch which is on or off. This reduces stress on belts and idler components used in the system.
Belt vs driveshaft, the belt is a potential slip point where the driveshaft is positive. With proper lubrication the shaft will well out live a belt.
The hydraulic lift is a great feature as it removes stress from an operator, many of the manual lift mowers are a little on the tough side to operate for a lighter operator.
Not all mowers have the ability to use hydraulic activated lifts or power attachments do to the lack of a pump to operate them.
Good seats are a must for many but a large set of tires with the proper air pressure will do a lot to level a rough field. After all if you don't fall into the hole then you can't feel it.