A friend asked me yesterday our opinion of the AutoVías double decker service from Pátzcuaro to Mexico City. Apparently he and his wife had only ridden on ETN.
For those of us in and near Pátzcuaro, using AutoVías is often more convenient. We get our tickets at the Central in Pátzcuaro and stay on until we get off at Terminal Poniente in Mexico City. As ETN doesn't serve Pátzcuaro, to use it, we first have to go to the Morelia bus station, wait a bit, then board the ETN bus.
Now there are some advantages to the ETN serices. The seating is better and somewhat more comfortable (although that on AutoVías is not bad, depending on your seat location), but because ETN passengers are given headsets, they don't have to watch the movie. That's a real plus!
The cost dfference, ETN slightly more, to most expats is negligible, especially when buying half price tickets with an INAPAM credencial. ¡Viva México! Mil gracias.
My wife, however, found that she tends to get motion sickness on the slightly swaying upper deck of the AutoVías double decker, so she chooses a seat on the "Ejecutivo" lower level. I, on the other hand, enjoy the better view from above, so we temporarily separated on our last return to Pátzcuaro. A different friend suffers from claustrophobia, and does not like the darker, confined spaces of the lower deck, so he always sits above, preferring the seat just aft of the stairs, as it has the most legroom.
More daring folks like the upper deck forward seats, with the panoramic view over the road. Yet another friend says wryly that he likes that front window seat, because in case of an accident, it will be over quickly, and he wouldn't want to be a burden to anyone. (This is his black humor.)
A quirk of AutoVías, noted on our last trip, is that despite having selected our seating on the computer at the taquilla, the seat numbers did not correspond once we boarded. However, there hapened to be ample empty spaces and we all were satisfied.
Another factor in choosing either service is that ETN has many more trips to México DF than does AutoVías. So, it might be worth the slight inconvenience for Patzcuarenses to transfer in Morelia Bus Station if they prefer a better departure time.
Onboard food: Fugeddaboudit. Bring a sandwich. However, AutoVías, and perhaps ETN, offer BOING!, a fruit drink of superior characteristics, and that's worth drinking. I will admit, that on our most recent return Mex-Patz, the ham and cheese croissant on AutoVías was better than edible. Still, the torta bought and the lunch stand at Terminal Poniente was better.
These are the websites for AutoVías: http://www.hdp.com.mx/inicio/
(But I don't recommend purchasing online. Sometimes the site malfunctions.)
Same advice about not purchasing online. However, ETN's site is more reliable
In conclusion, this is still an imperfect art, not a science. Someone needs to write a mobile app. ;-)