It's been awhile since I've played a Blues Harp, but it seems to me that back when I used to play both Blues Harps and Marine Bands regularly I didn't find much difference between them - I think the Blues Harp name was more of a marketing gimmick than a reflection of any unique properties of the instrument. Proviso: I'm not an expert either, but I'm willing to run off my mouth till one comes along.

BTW, I'm not so crazy about the Lee Oskars myself ... One of those "matters of taste" things ...