I would probably switch if AA lost MRTC. I currently will pick AA at a higher price because of MRTC ($100 or so definitely yes, $1K definitely not, in between depends on flight length etc).

For example I routinely fly AA for BOS/SLC instead of Delta (connection vs nonstop) because of MRTC.

Without MRTC, I would pick UA E+, then other carriers with better pitch than LRTC, then whoever was cheaper. AAdvantage wouldn't win me over; I never get to use the miles I already have.