Agree, wrong tip on the DBA, harshness ensues (for me, Ety triple flange completely solves it). But the channel imbalance should not occur if the phones are not defective. You might have tried this, but what about different sizes. I know my ears are different L to R because of the custom sleeves I own (you can see it). I have in the past used one size on one ear and another size on the other. Could be a solution for you in terms of channel imbalance. As for sibilance, unless you can get rid of it via tip, the DBAs may not be for you. If I was stuck with short tips, I would not have kept mine, for example.
Anyway, we are off topic here, as this is an SM3 v. 535 thread. Not a DBA vs. SM3 thread. So back to topic. It is interesting, and the 535s would be a consideration except they cost too darn much. I doubt they are $300 of an improvement over the DBAs ( as a $500 custom might be).
sry for sidetracking.. that was just an example of how wrong tips or wrong insertion can affect sound.. i do notice at some certain similar depth, i'll get the channel balance.. that's already personal ear problems tho.
i agree that $300 is not gonna give THAT much improvement.. but sometimes those little2 tiny things in music, that mere 5% extras would combine everything to give 200% satisfation when listening..