My experiences in no particular order:
Bushog size is a function of how much time you want to spend bushogging. Buying a tractor to fit an existing bushog is not ideal, better to get the correct tractor for your use and then replace the bushog if needed.
If your land is not flat, the width to which you can spread out your rear tires is very important. Compact tractors (my first) are often very tippy (not good on slopes) as the tires were at less than 40" with no way to widen them. All it takes is not seeing one rock on the high side or one hole on the low side and you can feel it start to go. I resorted to driving around with my backhoe outriggers almost down, but obviously you can't bushog with a backhoe. My second tractor (full size) is set out over 90" at the rear tires.
Should have bought a midsize or bigger initially...
On non flat land a loader needs 4x4. Otherwise you have no front brakes. 4x4 allows rear brakes to slow the front axle when engaged. Also if you pick up something heavy and don't have 4x4 engaged, and you start down a hill watch out! No fun when your back tires lock up but all the weight is on the front axle so you pick up speed... you don't quickly forget again.
I would pick a tractor based on frame size first, then determine what HP engine I want with that frame.
Intelligence is a must. Tractors are dumb. They will hurt you. You need the wisdom to do a job correctly and safely. Keep kids and onlookers away. A "safe" machine sized to the task helps. Hard to be safe with incorrect equipment, especially when tired and trying to finish.