My two copper bits' worth:
1) You should always make or play the character that you most enjoy. Otherwise, you won't invest the energy and time to be good at it, and then you'll still have nobody to play with. ("Don't invite HIM, he'll use AE's when he shouldn't, and pull every mob in the castle - remember last time?") More importantly, as this is a game, and supposed to be fun: playing a character which bores/frustrates/confuses/irritates you diminishes the fun, right? Bah to that!
2) Ye have other character slots, use 'em! If you're not familiar with the classes enough to know what they do/what their playability is, then experiment. Takes what, a weekend to level up to 10-15 or so, particularly if you've leveled up another character already and are familiar with game mechanics? I strongly recommend that, if you try this approach, you go to 20 or so. Paladins, for instance, are pretty much hack, hack, hack, til about 15 when you can start blastin' undead, etc...
3) Think about what kind of player you are: solo/group/raid-oriented, and how "busy" you want to be in a fight.
My main is a paladin, as I find they match my personal ideology of doing the right thing.. well, because it is the right thing. I also enjoy that, with careful planning, I can solo moderately well. Being a single mom of a 4-year-old means that it can be tricky, during the majority of my game-time, to devote my full attention to the game required for soloing another type of character - and it's not fair to a group to keep having to say "Afk a sec, the boy wants another drink of water (or a hug. or a stern talking-to.) before sleeping."
However, when a friend (who was leaving the game) gifted me with a 60 chanter on Live, I took the time to learn to use it, and voila! I discovered that where raids were B-o-r-i-n-g as a paladin (particularly if you're secondary tank-ing and the raid has enough healers), they ROCK on a chanter. So Yuna became my raid character, and became highly requested by the guildies for groups, too, while Lark was my solo char, and great for duoing with my ranger (now former) hubby (I swear he just played a Ranger so I would have to Lay Hands on him more often).
Soloing the chanter, though, even at that level, just wasn't fun for me. So it depends on what you're doing, and where and how you want to play. Sometimes, you'll find that you keep one character for a certain mood, and another for other purposes.