If you have Northern Tool in your area, you can go observe both the ProCom and Mr Heater Big Maxx in same store.
When I looked at both in my area, I thought ProCom looked cheap, while the Mr Heater Big Maxx looked fine. At only $399 for the MH Big Maxx, I'd go with that one. Lots of GJ people have MH Big Maxx and have pretty good reviews.