I'd vote for hydro, as it is a real marked improvement over the 'old' gear technology (amazing what improvements and progress we've seen) and HST seems to be pretty bullet-proof and holding up well.
Gear used to work, and will still get you by, but even when working with the drawbar, backing up a wagon or trailer with HST is a breeze compared to the gear. I have very few chores I do that HST isn't better, and if I have long steady pulls of anything, I just use the cruise control and have the 'gear' feature. Brush hogging is a breeze with HST. So manueverable in the woods, backing into spots, working slowly around trees and other obstacles. The HST gives you the fine touch in movement that the gear cannot do, and forward/reverse is a no-hands manuever, rather than a hand shifting manuever. I like it, can you tell?
Tilling (often it is pushing you rather than you pulling it) is much better with HST rather than gear, IMO and from a fair amount of experience. Yes, gear will get you by, but sounds like the dealer is trying to help you make the best decision for you (probably him too), IMO.