I have a 15 year old JD275 48 inch 17 hp kaw, hydro. No problem. I have a 10 year old husky varni, 48 inch 23 hp briggs, 350 hours, hydrostatic, no problem.
Todays mowers you have two choices, a hydro or a tranney with 2 belts and a pulley that changes size to vary speed. IMHO, the hydrostatic has way more pulling power. The 2 belts won't hold up if you need to pull hard and the pair of belts aren't cheap. I have an old troy-built 46 inch 20 hp briggs with 500 hrs on it. Learned the hard way, the two belt tranny is crap for pulling. George