One question I have is why should the DL reply effect your future booking decisions?

DL is going to send you a few thousand SkiPesos. This really means nothing.

But the reality is you obviously do a lot of short haul flights in the SE. My guess is that DL has better schedules for you. Thus you will spend more time at home flying DL than others.

If after reflection another carrier is better for YOU, then you should switch regardless of how DL replies to this letter.