Taking Votech classes only work for HVAC because they do not have the licensing requirement plumbing does. However, this may not be a bad idea as many plumbing companies are in HVAC also.
Depending on how old you are and financial situation, you may want to consider the union if one is in your area.
If you want to work non-union, you will find that plumbing is very much a sales job and besides, you get paid to work on other peoples plumbing. Having good people skills is a must for residential/commercial service work. The technical skill will come with time.
Regardless of what you decide, have fun…I too became a REAL plumber after a career change.