I support paladin as probably the BIS non-raid tank. The utility it brings with blessings + auras, as well as its aoe threat management (in part due to blessing of salv), just tops everything the warrior or druid is going to bring to that group, since what the warrior excels at, isn't really needed in dungeons.

Unless you want a warrior specifically, if you just want a better tank for running dungeons, I'd go with a paladin, I'd even go with a druid over a warrior I think, since a druid can generate aoe threat even better than a warrior as well, and is completely adequate for dungeon tanking.