I have found that DuPont or Ditzler/PPG paints are much superior to most anything out there when it comes to durability and long lasting finish, when proper preparation has been done before spraying. Any paint will look good when it is new, the difference starts to show after a couple of years. It is just a matter of what results you are looking to achieve. Say if it is just a hobby machine and all you want is some fresh color most any paint will do the job just fine. The machines I have restored for show got the best quality primers and paints I could find because of the extensive labor I invested in the preperation. Absolute cleanliness is mandatory or even expensive paints won't perform. I have sprayed cheaper paints as well as the top of the line and can without a doubt say you do still get what you pay for.
No.9 Auto Patrol 8A331
No.9 Auto Patrol 8A539
Minneapolis-Moline prototype crawler X253
1945 Farmall H
1923 Fordson on Trackson crawler conversion