I have used my TA exclusively for several years. As for personalized service, I find that it is the service after quote and booking that counts the most.
My TA offers suggestions on packing, child safety, restaurants, etc and is pretty much accessible 24/7. The last two trips my TA had my trip discounted and I was emailed before I even saw the discounts posted on the DIS.
When the new dining information and CRT changes came out a few weeks ago, I got an email first thing that morning telling me about the changes and new policies even though I do not have another trip booked as of yet.
Just like picking a doctor or any other service provider,a TA is very personal. I had shopped around before finding the agency I use. I found that talking to the agents gave me a better sense of what services they would provide and how accessible they would be rather than the first chatty email I got.
Good Luck picking an agency. It sounds like you have lots of choices. Just remember that all of the agencies you requested quotes from work on commission....you may wish to politely let them know you are no longer interested in the quote they provided so they do not continue to work on a quote that will not be booked!
June