i believe bobamaker's pack is a little smaller than MOW's....plus, shipping costs... i dont think MOW's comes with a harness, but that is where i come in...:cheers both jetpack's are amazing, so really, i recommend buying the one from the side of the pond you are on...saves $$ on shipping...
The short answer? The makers. It's like saying... Why BMW's and Mercedes' cars are diferent? They both have 4 wheels, an engine, exhaust, etc., so where the difference is between both?
Some persons like BMW and others the Mercedes, both are the same but with some little differences.