LotRO player's guide to WoW: World setting
There's no denying that the lands of Azeroth and Middle-earth are literally worlds apart. While J.R.R. Tolkien created Orcs and Elves as we know them today, Blizzard refined these definitions into their own Warcraft lore (with a little help from Warhammer along the way) that is far from anything Tolkien could have imagined.
World of Warcraft's setting could be considered wild or exaggerated fantasy, with purple trees, flying gryphons, shotguns and motorcycles. Lord of the Rings Online, on the other hand is grounded in a more "realistic" fantasy setting. This is quite possibly one of the most polarizing aspects of either game, as some people just can't stand one or the other. Also, since the use of magic in LotRO is usually frowned-upon (although that's slowly beginning to change with Moria), WoW flaunts its magic-use every chance it gets. There are very few restrictions when it comes to what type of fantastical evocations you can experience in WoW.
World of Warcraft also takes full advantage of the "good vs. bad" mechanic with the Horde vs. Alliance. There really is nothing like that in LotRO, as Man, Elves, Dwarves and Hobbits all get along fairly well. LotRO has Monster Play, which is their take on PvP in a closed map setting, but it's really not the same at all. In WoW, the open PvP allows players to attack each other with a simple click of the mouse. Any hostile activity (including healing someone who is engaged in PvP) is considered grounds for a PvP flag. In LotRO, if you'd like to fight another player in the open world, you have to agree to a dual, and even then, most people just don't do it. You don't see very many groups of players killing each other at the entrance to large cities (I'm looking at you, Orgrimmar), and duel requests are a rarity. This is actually a major difference between the games, and it keeps LotRO firmly planted within their reputation of being mainly a story-driven game. We will touch more on the PvP comparison later, but for now, let's move on to the class comparison.