For what it's worth here's what I think, there are several places to get involved with HWLG in MP and/or PBEM format, if I were not already a member of a grounp I would check them all out and find the one that suited me best, for whatever reason, then concentrate on that one.....trying to spread your time over many different groups and forums is not easy if you have a limited anount of time.
I'm able to play HWLG at many different times of the day and night, which fit in with different time zones, but I mainly play with NBC members becasue they do go to the trouble of arranging games.
Sitting anywhere (steam/xfire/teamspeak/forum/IM) waiting for a game is not a good use of time, with a day or so notice a game can be set up in a few minutes, if people have a few minutes to ping off a PM or a e-mail.
I have a game arranged for 8pm tomorrow, and another for 1pm on Tuesday, they were easy to arrange, setting up MP games is not hard to do, a couple of e-mails or PMs on the forum, or even a post on the forum is all it takes - IF people are interested.