Sounds like we both are fans of the 1RBT MK2. I ONLY used my MK2s in APTX mode and playing FLAC off my Note 4.. IMO, that is where the MK2 shines, when fed hi res audio/flac files across bluetooth from an aptx supporting source.
Also, like you, anything that Sony comes out with and states it is better, successor or upgrade to the MK2, THEY GOT ME!!
In the near future, I will be getting the 1ABT, the Senn M2 and the Def Tech, going to keep ONE of them..I never had a NC set of headphones, so the M2 and the Def Tech are going to be real interesting for me to test. The 1ABT doesn't have NC.. Will see on them too. BTW, my MK2 is not going anywhere no matter what else I get.. .
I used the SBC mode on my PC before i got my aptx dongle
But now, both my PC and Phone have aptx
What I'm curious about the 1ABT is the new LDAC codec. Not sure if you would need a specific hardware for that or could be upgraded through software update.
I know that the Walkman NW-A16 and NW-A17 will get LDAC support through update in April, so i kinda hope LDAC support can be achieved too through Lollipop Update on my Phone (Xperia Z2) when it's out