First two answers are good advice. I had a 4 acre block, flat/gently undulating. I had a John Deere 20hp V twin with 48" cut, side discharge also had mulching capability . Lawn area 2.5 - 3 acre, approx 2 hours cutting time.
Engine Briggs & Stratton with cast iron sleeves in bore
Commercial/Industrial engine. Also had cruise control and what I used as Beer Can holders
Many brands of reliable engines, main thing is it is a Commercial/Industrial engine
Hydrostatic is like an automatic gear box had a forward and reverse pedal.
Geared Models you use a clutch and select the gear
When you find a mower you like get them to come to your place to do a demo and let you try it out
Once you have your mower follow the maintenance schedule exactly, wether you do servicing or have dealer do it you are protecting your investment and ensuring it lasts for many years