I have my own separate folder in Google Reader for webcomics, as well as the "Subscribe" button in my tool bar to easily add webcomics with RSS feeds to my reader. It's quite nifty.
Over the past few weeks, I've noticed that the comics I've been adding the most are journal comics. In other words, comics that detail the life experiences of those who draw them.
The main difference I've noticed so far is that journal comics tend to be a lot more narrative; in other words, the person takes the time to briefly describe what they did instead of showing you what they did. And yet, somehow, the majority of these comics manage to not come off as preachy.
In addition, they seem to cover much more ground in terms of story and life events. Eeeeennnnteresting... Wondering if I should experiment with this kind of format...