Some ZTRs with rear discharge as standard equipment have longer frames to accommodate the deck, the deck suspension may be different from a side discharge machine. I have a Hustler X-ONE with a 60" rear discharge deck, but not familiar with a side discharge X-ONE to compare.
Most rear discharge decks have at least one blade that turns opposite from the others. This is done on the deck and not by the machine.
My Hustler is used primarily for cemetery mowing where the rear discharge deck is best utilized around grave stones.