The visiting teachers don't stay around long. They take the money and run. The local teachers are around for continuity and charge less.
YouTube is a useful tool if someone doesn't know the teachers. What you see in the videos is usually what you get in classes. If you want to improve as a social dancer, avoid classes with teachers who want to perform more than teach.
The best place to look for a teacher is in the milonga. Most teachers don't dance socially because they are too busy teaching. Dancers are spending lots of money taking too many classes and not learning how to dance.
Usually outside the BsAs there are AT schools with a certain style of dancing and the teachers of that schools are also organizers of the festivals. Local teacher normally call visiting teacher in which style they prefer and teach. So it's common that local teacher learn "basic" technique and visiting teacher improve that basic technique and add something of their own or present interesting ways how to use that technique in various combinations.
Also those local teacher have their schools and organize milongas and practicas.
Students knowing local teachers could know what to expect from visiting teacher if they know the organizers i.e. local teachers.
I agree with about taking to many lessons and not learning how to use everything cause a lots of that material is forgotten or not danced during practicas and milongas.
I am just saying how it is tango communities outside BsAs