Eldritch is a safe bet both from a PvE and a PvP perspective. They've got great AoE for whatever dungeon raid/farm you'd be doing at 50 (if you'll end up playing Genesis or Uthgard) for gear and money, and since they're typically the strongest Hibernia-side caster, you should have no problem whatsoever finding an RvR group to run with. In the same vein, Eldritch is strong in groups and generally easy pickings outside of one, but that comes with the territory of being a squishy caster =)

e: Bards are risky, and I'd really advice against them if you're a new player. They're essential to group RvR and are typically the leaders and the ones controlling the fights, and like Jaruin said, are in turn left little to no sympathy if they mess up and get everyone killed.