I really doesn't make sense to compare OS X versus Windows given the history of both parts of OS X (OpenStep and Mac OS). Mac OS was available on clones and didn't expand the market at all. OpenStep was available on multiple platforms from multiple vendors. Neither gained market share. To be fair about it, 1984 was a little too late in the game as the C64 was losing share, Apple was already pretty low (both II and Mac), and Microsoft already had a hefty advantage [1].

[1] http://arstechnica.com/old/content/2005/12/total-share.ars/5