I talked to a few different TAs around the beginning too and it was an easy decision for me to choose because all but one had problems returning my emails even though they were all 'Destination Weddings Specialists'. When I found the one I am currently using, she was always quick to respond to my emails and she got me some test quotes before I was ready to book which were better than I could find online so I knew she was the one and stopped my search.
I definitely recommend to look around and be honest with your TA. If they can't deliver, they have to understand that you will want to look elsewhere. Judging from these forums, dealing with a bad TA is an awfully stressful experience and something I want to avoid!