In my experience, balsa machines differently than poplar. Even though it's classified as a hardwood, the grain tears so easily I've never had much luck getting a router to cut it well.
It sands so fast, I just use a piece of PVC pipe, split in half, with sand paper on the inside, to round balsa baits.
Hazmail was the first one on TU to use this method, that I know of, and it works like a dream. Plus it's cheap, and so am I.