Having flown from PVR recently on both DL and AS - I can say that the DL lines are definitely shorter but its likely because the load factors are abysmal on DL. On a PVR-SEA flight recently, we had less than 20 people onboard while the AS flight I was on had about an 80% load factor. The bottleneck seems to be mainly on people not doing the advance work - as if everyone uploaded stuff to Verifly on AS, it would be very fast. DL does a poor job of marketing that you need to upload to TrustAssure which makes their process slow as well but due to the small number of passengers they seem to be carrying, it makes check-in not so long. I really can't imagine what DL lines would look like with 80% load factors on their Mexico flights - I heard a report from CUN this past weekend of over 1000 people waiting to check-in with DL and it taking over 2 hours.

I'd say the best I've seen flying out of Mexico recently was UA - they have you upload everything directly in the app to their Travel Ready center (Covid test and Attestation forms) and you could have a full contactless experience and use Mobile boarding passes even. If you are traveling to Mexico, save time by going to vuelaseguro.com and enter your arrival and departure information to get the Green QR code and breeze through the airport arrival/departure checks. Otherwise, you'll end up scrambling like many other people to do it at the airport or fill out the paper forms.