I just dinged 69, and I've only quested in three of the Outlands zones. Should I keep questing in Outland, or should I move on to Northrend?
If you have never leveled through the Outland content before it is certainly worth your time if you have an interest in the lore.
Also if you get a lot of this content and levels before going to Northrend, then when you get to to Northrend you will reach level 80 faster. And then when you're 80 you will still have a lot of quests in Northrend to left to do and doing all all of them at maximum level turns into cold hard cash.
That depends on what you really want. If you want to get to 80 fast and experience the WotLK content, go to Northrend. If you would like to get the most of the game however, definetly stay in Outland.
Another thing is - are you on a PvP server? If so, you might consider staying in Outland for a while as people leveling in Northrend (and being level 71+) will definitely want to gank you a bit ;) And if you are a PvP player you will probably want to be 80 asap, since then you will be able to fight in the Arenas. If you enjoy PvE more, try the Outland dungeons too, they are nice (i liked them even more than those in Northrend, especially Coilfang Reservoir dungeons).
Personally I would (and did) go to Northrend.
I found the levelling experience to much quicker - more XP from mobs and quests, plus quests are in definite "hubs", making it quicker to pickup and hand-in quests.
On my Paladin I made sure to complete all the quests in both WOTLK starting zones. This put me to ~73/74 from 68, without too much effort. It was also a great way to pickup rep, gear, and gold!
If you want to see the content, staying in Outlands is nice, but questing experience has improved a lot in WOTKL and the gold/XP reward will be higher too. It’s cheaper to fly in Outlands too (and impossible to do in Northrend unless you are level 77 or have an 80 and 1000gp). Flying makes questing faster and less prone to be ganked by mobs or players when applicable.
I’d go to northrend. But that’s because I’ve done all the outland quests at least on two different chars. Some up to 10 times ! :)
i shorted myself and basically did the leveling from 70-80 via battleground XP (before it got nerfed, Alterac Valley was a cavalcade of XP). if you're looking to get Raid Ready and see ICC before Cataclysm comes out (and Raiding moves on to the next big thing), I would recommend a) queueing for whichever BG seems to net you the most XP, b) running your daily RDFs, and c) questing in Northrend so you can also get your professions up to snuff. sure, you'll miss out on the lore and story. personally, going back and overpowering it is still satisfying and the money from quests is just as good.
Northrend if you're level 69. You will level a lot faster. Bigger XP for the trash mobs. and the quests are more plentiful.
It depends on your objective. You want to get to 80 in a hurry. Then start in Northrend. You'll get larger XP rewards for quests. If you just want to take your time with the Lore/Legend, Then keep complete Outlands.