I dont see a difference except design. I bought a UMP. I have it sitting right here with me. Its great in quality! All the aluminium welds are perfect. The only thing you have to do is modify your oval intake hole in your box to a round hole for the 3 inch rubber intake hose. The UMP bolts in two locations on the motor, giving it great structure, and the filter is easy to change. Everything you need is included with the setup.
I dont know much about the others, Im sure they are good as well, but I went for the best bang for the buck option and Im extremely happy I did.
Great Job UMP!!!!!