For that size lot and steady slope, I prefer a stand-up model with sulky/velke/jungle wheels. The standups are lighter which means less rutting and lower fuel use. Things to compare are pump size/quickness, spindles, deck thickness, and personal fit. I like a floating deck for better cut quality on bumpy areas. Another advantage of a standup is your knees act as shock absorbers, rather than your back on a riding model.
I like SCAGs, both Sequoyah and Homestead are good dealers. Just like with outboards, you want a shop that has the ability to quickly service your mower, when the need arises.
Also watch Lawnsite and craigslist to follow used prices. High quality mowers sell for more used, even with high hours.
