It is inconceivable that an onsite finish is as durable and is the quality of a humidity/contaminant/explosion proof controlled finish room in a modern cabinet factory.

Sealed MDF is very dimensionally stable and an excellent substrate for paint. There are plenty of pictures of cracked painted plywood on this site alone.

Paint 'em in the garage with the door open and the guys cutting concrete show up five minutes later.

Read up on KCMA testing programs and what it takes to get a line certified. Then ask the local slap paint on out of a can guys if they will guarantee theirs to hold up to the same abuse. Then have them supply and test it. It won't hold up. Factory finish with a MDF. Center panel all the way. Maple stiles and rails. No alder or poplar or other cheap soft wood.

I was recently given a 10-day Bluebook free trial. Bluebook charges subcontractors a subscription fee for access to commercial plans and specifications. One GC was looking for a cabinet company that had or could get their cabinets KCMA certified. They couldn't bid without it.