I assume you are preparing to paint, yes? I don't have a lot of experience with preping for paint, but a professional stitch & glue boat builder that I know told me once that he declines to use high build primer under his two-part epoxy finishes. Said he finds that they "compromise" the finish because the ease with which they chip. Perhaps its a greater problem with a boat that is brought into a dock regularly. But based on his comments, if it were me, I'd go with micro balloons.

: Once I sand my Arctic Tern, I know I'll have some areas that require fairing.
: Maybe 1/3 of the boat. Should I just rely on another coat or two of epoxy
: with micro-balloons or can get by with some high build primer. If I need
: to go with the HB primer or both, which primer would you recommend?