Personally, I feel the wheel/castor system on the midi is more robust than the fein. Those little castirs dobt inspire the most confidence in me vs the larger wheels+castors the midi has. I don't have any experience directly with the fein; however, I enjoy the additional cohesiveness that festool provides with their tools. The stacking of the systainers was surprisingly useful. The bags are only 4 gal and more expensive, but I have no problems reusing them as long as what I sucked up isn't hazardous ie lead paint. My last bit of reasoning, which may seem a little frivolous to some, is that I like having my green tools with a green vacuum XD For me, $100 was worth the difference. (I actually scored mine off Craigslist for cheap, but I would be willing to front the extra 100.