By the time you have them at that level you should have a pretty good feel for which one you enjoy playing the most. Your Warrior will be looking for almost the exact same gear your Paladin did as a neo 80, as will your DK, sans the Shield and 1 Hander.
Personally, I've got an 80 Paladin and 80 Warrior, and working on a 52 Druid to 80 before Cata. It took me to 58 to realize I didn't like the DK playstyle.
my biug problem was back when the heirlooms came available i got cloth bescause i wanted to level my warlock at the time but i quickly changed my mind and wish now i had plate .
Pally is fun but i do find in boss fights warriors overwhelm me my last raid (my first time playing her since 3.1 i found it quite difficult to steal aggro from the MT warrior (Who i admit was over geared then me) when we had to switch aggro in the Gluth fight.
Do what's most fun for you. You've still got a lot to do on your paladin. I've got an 80 warrior, an 80 DK, a 71 Paladin, and my druid is only like 36. For me, I think the warrior is the most fun by far. I have a hard time enjoying myself as much tanking without Warbringer. I think it's the best thing that ever happened to WoW.