You should look at what implements you want to use first,ploughs,power harrows,sprayer,post hole digger,water pumps,etc.
Two wheel drive or FWA,front blade and remote hydraulics.
Time spent in the field to do the job.
A lot of clay soil here so timing is everything.
Too wet or too dry.
Will it be stored in a shed,are rats a problem with chewing wiring harness's.
Will you have a pressure water cleaner,grease gun and air compressor to maintain tractor.
The Kubota 34 and 47 horsepower are most common around here although not unusual to see the tractor bonnets up from overheating,working to hard.