I use Patrick Rauland's version of the deploy script: https://gist.github.com/3767319 otherwise I don't think I'd have plugins in the repo... or wouldn't update them. I can't seem to get my head around SVN, but sort-of understand Git. I've been able to easily submit features or bugfixes to other github-hosted plugins and have had a few people do the same with mine; something I haven't done with SVN. It is just a matter of personal preference.. and probably what you use first.

If you want lots of people to find and use your plugin, then the repo is the place to be. Of course, that also means a ton more support issues will crop up.