If you are plainng to charter in the future, I'd definitely go to a school
with ASA or US Sail certification
. There are some charter companies (Croatia) that are now saying they will no let a boat out without a certificate.
The nice thing about ASA and US Sail, the courses are about the same regardless of where you take the classes. Now the instructors, that is another matter. As with any class, you will get out, what you put into the course. The more you study the books
, learn the knots, ahead of time, will leave you more time for learing about sailing when you are in the class.
Lastly, ASA can and has removed their certification
from sailing schools that do not provide training to their standards.