I had a listen to the different EH Qtrons & didn't like the whishy whisper sound that they seem to give everything.
I love my mf101 & although the filter amount only works upwards, can be gotten around by taking a patch cable from the env out & back into cutoff in. Or use an expression pedal (or 4).
I also find it adds more bass to the sound & you can even add analogue overdrive to the sound.
Downsides to the pedal (if you wanna call em that):
If you turn the drive up to give you some OD, it can't be turned off with the bypass (not true bypass) or linked to an exp pedal.
It's big. & with a couple of exp pedals it could take up most of your board.
None of these are negitaves to me tho as I usually use the mf105b for OD (& other things) & only have those 2 pedals, 1 exp pedal ( but gonna get another soonish), a tap tempo for the 105b (which sits in front of the corner of the board) and a boss chorus (which I have borrowed to try some swishy pad like sounds in conjunction with the moogs).