I have always used both products for the same basic purpose. I would put three coats on, sanding between each coat, to get a smooth fin with no wood grain showing when I painted them. The only difference I see is that sanding sealer is clear while balsa fiillercoat is white.

I have had good success using both of these products, but I was just wondering if anyone had opinions as to why one might be preferable over the other. They both seem to do the same thing in my eyes.