For me, this isn't great but ok. I don't really know all the differences, but have always seen loyalty programs as a bonus and accept the good times (SIN runs on UA to make SE purely on miles) are long gone. I have MM, fly a decent amount but not enough to make SE these days. The gradual changes in upgrades and especially the reduction in R now means I buy more J internationally (where there are deals) and use UG domestic where/when there is R. I'd still rather fly an airline I have status with (and get some benefits from) and collect miles from different sources to one program. I've not flown Y on AC since the early 2000s. So I will be still be flying AC.