Ann, by all means compost the pulp.

As for the difference in yeast activity, it is possible that you did
not stir (shake) the pitchable yeast sufficiently before inoculation
and most of the yeast went into the apple and very little went into
the crabapple. Just a possibility....

Jack Keller, The Winemaking Home Page
http://winemaking.jackkeller.net/