Birch and maple both take clear coats very nicely so there is no issue there. However, in my opinion, maple looks nicer. Grain has a little more definition and is whiter. Birch grain can be quite bland is a a little on the yellow side. I don't work much with birch, preferring to use maple, but when I do get it, it is rare that I get a board without any brown to gray streaking. If you haven't yet decided on a clear coat, use a catalyzed lacquer or conversion varnish. It doesn't yellow like poly, varnishes and non-cat lacquers, keeping the beautiful maple color unchanged.