Depends what you're looking for I guess.
If you can do without the B6 synths (the m90 has 2 waves, but they are more limited in features than the ones on the B6), prefer dials over a touch screen and care not for the ability to mix and match whatever effect you please, then perhaps.
Then again, from what I've heard so far, the m90 doesn't sound any better or worse than my B6. They're also about the same size and both run fine from my powerbank. Had this been released before I bought my B6, I might have been tempted to buy one. But I see no reason to drop my B6 really. I like the m-90 (been looking for the older version for ages till I got my B6) but I currently have no need for 2 multi-pedals. But, as with everything YMMV.