in reply to My preferred version control system is...
Since I'm pretty much the entire IT department myself, there's generally nobody else making edits. So I keep one "production" copy, which I don't edit, and of which I always make a backup copy (usually with zip) before upgrading it. I keep one "development" version, which I edit directly, and which I periodically (when it seems stable) copy over to upgrade the production copy. Plus backups, which I definitely don't edit. So at any given time there's only one (1) copy that may have changes. No differences between multiple development versions means no merging.
Obviously this approach won't work so well for large teams of developers working on the same project simultaneously... but it works for me :-)
My dirty little secret is that there are some projects where I know I'm basically the only user, and in those cases I generally don't bother keeping a separate development version: I just edit the production code directly. This is not a practice I particularly recommend, but out of laziness it's what I sometimes end up doing.