Is communion service at the rail vs. in the pews a function of denomination or church size?

In the small baptist churches I've been a part of, (and the LDS service I attended), the communion elements are served to worshippers in the pews. In my Episcopal church, everybody comes up to the rail. I'm wondering a bit about how this variation in practice arose (Anyone know which came first?) and if there is a way of predicting how any given church will practice it.