Buying a new trailer need tips

I am looking to get a 4x6 or 4x8
this is NOT a TM or even a carpet cleaning rig.
I sell CC equipment so it's for that.
hauling around 2 or 4 portables new in box or a skid of air movers etc...
In winter I sell ice melting products so I need to haul a skid that weighs 2250LBS.

My question is about doors, floors and tires.
Does door style make a big difference?
Tires is bigger better? 12" vs 15"

thank you.
Ken J