I am a TA and only on one occasion have I not been able to match the VTG price for my passengers... after spending an hour with them on the itinerary and giving them the lowest rate available to me ($30 pp more than VTG) ... I left it up to the clients and told them no hard feelings if they booked with them this time but to keep me in mind for their next vacation... they were back the next day to book with me as they felt my honesty and willingness to stilll help them despite the possibility of not getting the booking made price less important.
All is great when dealing with them... but I would like to see what they would do if they needed to write a complaint letter on your behalf post cruise.... would you still receive the same service?
If the price is the same through a local travel agent, why would you book online? The $$ earned in your community is subsequently spent in your community.