I agree to the above, have a look at the servers clans/website and requirement list and then search http://www.armaholic.com/index.php or other sites listing mods to get the information. Gives a good sign of what's more popular, I dont know your experience, but search for a mod launch tool to be able to switch mod lists and login to servers meeting the mod groups requirement they need so not to get kicked.
Six updater is a good install to cover this, becuase not only does it host updates for most mods/online mods to keep track it lists many too.
Mainly let the server dictate the choice I would say, or narrow down the servers you frequent to make the minefield a little less.
I know thats not direct list, but just a tip for MP and mods