At some point in its history, the term 'sci-fi' picked up a somewhat negative undertone. Probably it made people think of dodgy b-movies where you could still see the strings.
And I have largely avoided using the term in relation to my writing because it appears to me that sci-fi nowadays is acceptable when it comes to TV and movies (thank you, SciFi Channel) but sf is generally used in connection with the written word. Maybe that is to encompass the broader genre of speculative fiction, or maybe it's just because well-read science fiction geeks want to separate themselves from casual Doctor Who fans.
Personally, I don't do fantasy as a rule, so I just sat on the fence and used 'science fiction' most of the time.
Which brings a whole new set of problems when you're talking about Christian science fiction: do you mean Christian science fiction, or Christian Science fiction? I would hope that a brief look at the contents of this blog would be enough to tell which I'm interested in, but it's a comment I've heard a few times, and it's true it might scare off a passing visitor. I skipped the issue in my website previously by calling it Biblical science fiction, which is arguably more accurate for stories based on the Old Testament, but is not really a widely used term.
The point of all this rambling is to say that I'm no longer concerned with being literary about my sf writings. Redeveloping my website seemed a good excuse to reconsider my stance, and I have decided: I'd far rather be considered a bit of an amateur when it comes to being a science fiction fan and author than have people think I'm anything other than the Bible-believing Methodist-Pentecostal Christian I'm trying to be.
Sci-fi is no longer a rude word.