Pay very careful attention to the application instructions for whatever anti-fouling
you choose. Roughing the surface is basic, but as SV Siren notes, there may be a compatibility issue, and there may be a wash needed before painting, or a temperature restriction, or a bunch of other problems that really need to be attended to, or you will end up with peeling bottom paint
, just where you can't do anything about it with the boat in the water.
First questions: Ablative or hard coat? Can you duplicate the make/model of the existing paint? If it is unknown, then the blasting looks more attractive since it lets you start from bare hull.
Think long term here. What will get your bottom off to a good start, so that future jobs are sand/roll only?