Played WoW since release on and off, mostly on. I've just cancelled my subscription to play LOTRO until WAR is out.
Reason for this is, i'm bored of WoW and its content, seen it all before, don't really want to carry on, PvP added a nice spice to the flavour for a while, but that didn't last.
Now as for LOTRO, right now i'm enjoying it as i'm playing with a bunch of friends and its fun. However, it is basically the same game, packaged in a different way with different skills and a different universe, the over-all game mechanics are very similar though.
At heart, i'm a PvPer, WoW's PvP just didn't cut it long term for me, and i've just done all the PvE before, so its getting long in the tooth. Lotro is new, and i'm enjoying the PvE, purely as its a different game, its PvP looks to be even worse than WoW's though, so I doubt the end game is there. But I shall just enjoy levelling up and playing with my friends until WAR is here to fulfill my PvP (RvR) bloodlust.
My suggestion to you is this:
If you want a game to muck around in for a good few months, playing non-hardcore, either game will do really, my personal preference obviously leaning toward LOTRO. Then when its out, hop onto the WAR bandwagon for PvP goodness.