Originally Posted by
chimambu
One that I can think of is that I lose any form of ability to influence the flights once booked.
Not entirely. Even with a TA booking you can do the usual MMB things, like seat selection, meal choice, online checkin.
(If the TA has not added your BAEC number to the booking, then just login using the PNR and surname, then click on "Add Frequent Flyer number".)