Reasons for preferring "transvestite":
1) More of a UK thing
2) Eddie Izzard
3) Sounds more exciting
3a) Sort of implies that there's more to it than just the clothes somehow
4) You can make puns about "TV night"
5) A "trans-" word like transgendered, transsexual - it emphasises the connection with (other) trans people
5a) There are at least two jokes that start "what's the difference between a transvestite and a transsexual"
6) Apparently Magnus Hirschfeld, the person who first coined the term, was very nice about us when he wrote about us - or so it says in My Husband Betty
7) One of my friends came up with the word "cisvestite" for a person who doesn't crossdress, I was amused by that
8) Everything sounds better in Latin
9) Did I mention Eddie Izzard?
Reasons for preferring "crossdresser":
1) crossdressers.com
2) Seems to be a better search term for finding useful information, books, etc.
3) The mental image I get of a transvestite is far too Rocky Horror for my liking - crossdresser sounds more wholesome
4) You can make puns about CDs, none are as exciting as TV night though
5) It just says what you are without too many connotations
Sometimes I'm in the mood for one, sometimes I'm in the mood for the other, most of the time I'd rather just be me.