Have you tried Global Agenda? I played it for a time, similar to both and has raiding (restricted to higher level players)
If you wanna test drive a tottally different game, I would suggest Team fortress 2 by valve ( the makers of steam, portal, left for dead, half life, and counter stike)
I posted something on this for someone else a while back, so I will attempt to tailor my post to your needs.
Please note the difference between free to play and free games. Most of the online games from large publishers (I am assuming you are not looking for simple flash games found freely and easily on many flash game sites) are free to play: you can register an account and play without paying, but up to a certain point (level, area restrictions, etc) or with certain disadvantages.
Most games allow you to play for free but with some slight disadvantages that don't really affect gameplay that much (lower xp gain rate, lower chance of epic drops, etc) whereas others have items sold in their stores that result in in-game in-balances (an extremely powerful weapon for example sold in the store only- if you want it you have to buy and if you don't and someone else does you are at a severe disadvantage).
I will attempt to list some of the free Massively Multi-player Online free-to-play games I know of and have played along with the aspects of the game that make it not so free...
Lord of the Rings Online: This is a great game, excellent graphics and recently went f2p (free to play). Huge player base. However, it really is f2p until level 20, after which the player will face major roadblocks in terms of advancing to the next level and completing quests (since this was an originally pay to play game, (I am assuming) quests were designed with the belief that the player buys certain high level equipment from the store to complete the quest), etc and also at every other 10 level after level 20. You are not required to pay a penny and can probably find ways to continue playing without paying but you will be left out of 2 main areas (where other quests are and major pvp's take place). Having said that, still a great game and lots to do on your own and you can probably (if you have the patience) continue on the f2p mode without paying for anything all the way
Dungeons and Dragons Online: Another game from the above publisher (turbine) that also went f2p recently. Has a storyline too (and I could say more intriguing and captivating than the LoTRO storyline). The game has a unique levelling up mechanism where you increase in ranks of your selected profession as well as levels. I think the current max lvl is 20 at the moment. I couldn't exactly figure what was going on Anyway, excellent graphics and gameplay. Fairly large player base. Not sure if there is level restrictions in the form of difficulty here.... but then again I haven't played this game for that long. Would recommend though.
Pirates of the Burning Sea: This is a very unique MMO in that you play in the 17th century Caribbean and can play as pirate (as the name suggests) or as a member of one of the colonial powers (English, French, Dutch). Colonial powers have 3 careers each with different capabilities and pirates have 2 classes. Player driven economy. Features land and sea battles. F2P limitations are 2 ships and 2 characters per account and 2 economy (building) slots. The building slots are too few to do any real economy so I would suggest becoming a pirate in f2p (as a pirate you also get the chance to capture an enemy's ship in regular looting and a 100% chance of capture at certain intervals in cut throat career of the pirate nation). You can use the 2 buildings to make expendable items (such as leather, which can also be traded with certain npc's for other and better items). Graphics are great too (although the characters seem a little cartoony), especially sea battles and ships.
Face of Mankind: Futuristic setting, f2p MMO. Several different classes and player driven economy. Excellent graphics. F2P limitations are lower xp gain rate, max number of clones (lives) you can have at any one time is 10 (these can be restocked below 10 but never goes above 10), stuff you make and build can only be upto medium quality (you cannot make high quality) but you can use any quality you like, including high quality.
Runes of Magic: This is similar to World of Warcraft in many ways than one, including graphics and game-play. In fact some people go so far as calling it a WoW clone. I am not really sure on the F2P limitations on this one... my cousin managed to go up to lvl 70 something on this without paying anything and is still playing.
One other game I should mention as well is Savage 2: A tortured soul. It is a little different than the traditional MMO in that it is slightly like counter-strike where you have to fight in a map and on each you can choose from 5 classes although not all open at once (some open as you progress in game). You have to fight on teams so it is more of a co-op game but against other players.
Furthermore, EA now has some free to play titles, such as Battlefield: Heroes (a 3rd person shooter game with cartoony characters) and Battlefield:F2P (like the traditional Battlefield titles, but online and MMO- you gain skills for your characters as you advance).
Also Age of Conan and Heroes of Newerth went F2P recently, but I doubt F2P players will be able to get much from these games as they were and are planned to get poeple to buy the game or, even better, buy items from the shop so ı do not know how balanced the game mechanics are in these. I am going to try Age of Conan next week after my schedule opens up a little, so I could post you an update on this then (pm me if you want?).
Actually there is a good site that gives information on free to play online games, including its pros and cons, screenshots, gameplay videos (if available) and f2p limitations. You may want to check it out if you feel you are looking for something else that we have not mentioned so far. http://mmohuts.com
On the other hand, I would also like to mention that there are also free (freeware) games (some are ad supported but most of them are not as their ad servers are no longer online) that are available from reputable publishers that have gone free. Most notable ones are:
Some of these games have multiplayer modes too so they are not only single player, but they are not MMO's.
Lastly, I cannot go on without mentioning that there are also Open-Source games that available these days. Some of these games have excellent graphics (though not as great as some of the more recent titles by the major publishers, but considering these are indie projects, they are really impressive). There are some notable ones, but I can't pull them off the top of my head. Mostly single player games with quite a few having multi-player abilities. You may or may not enjoy these however, as they are mainly indie projects.
Hope you found this information helpful... have fun