I played FFXI for roughly a year before making the switch to EQ2. My answers will be brief as I am at work, but if you look back a couple of pages you will see other threads with more detailed replies.
Leveling in EQ2, especially at lower levels, is much more fun. A good chunk of your xp comes from quests, and when leveling you don't just sit in one place killing crabs. Instead you often work on completing quests as you level, and that takes you through entire zones or dungeons to do.
Its hard to say about endgame content, because people are literally just reaching 50th level now. There is a good chance that FFXIs endgame is more fleshed out as they have had two years to do it. However, EQ had the most detailed endgame of any MMPORPG, and I expect that EQ2 will be the same. There are only 50 levels right now, but rumors say it will go up to 200 eventually.
I can get 10-15% xp an hour or so while soloing at level 34. I can get double that in a good group. So soloing is possible, but definitely slower than grouping. And any class can solo, really unlike FFXI where only beastmaster could.
The best pair for xping would be a healer and a tank. Brawler + Shaman flies through the game in my experience. Though, of course, a full group is still better xp.
Hope that helps...