Comparing the 17 series from bitmain to any other mining gear will always lead to the same results, those 17 series are the worst mining gears anybody has ever made, so without a doubt, the M20 and M21s are far more robust than S17/T17, but since we don't have enough data on S19/T19 we can't be certain about their quality, my bet is "they are much better than the 17 series", but are they better than the m30+/m30++/m30s from microbt?  nobody can tell, it is a bit too early to judge.

But overall comparing Microbt gears to Bitmain in terms of quality, I would say MicroBt, honestly, Bitmain failed big time in the 17 series, S9k , S9e and many other non-btc mining gears, the S9 was the last mining gear from Bitmain with tremendous robustness, I hope they have gone back to the same standards on these 19 series, although I wouldn't trust them until months have passed.