I bought both. WotLKs first 50 DK quests are not to by missed.
However, Moria is outstanding and just as worthy of play. There are a lot of people leveling their new Rune Makers and Wardens so the influx of new people to the game have plenty of company in the starter zones. Moria has started a renaissance of sorts in LotRO and the game is at a peak right now. LotRO is the most underrated MMO on the market. If Turbine had made a different decision in regards how they implemented PvP, LotRO would be a close competitor to WoW.