People (especially Diggers, I think) like to compare Digg and Slashdot in various areas (and often say how one will kill the other). This comparison has always struck me as baseless, but I’ve never seen anyone saying anything about it (yes, that may be because I haven’t looked :P), so this is what I think: Digg and Slashdot are two very different beasts, and comparing one to the other is very much like comparing apples to boobs. Sure, both may be firm and round, but, well, it’s just sick. Plus, babies can’t eat apples.

1. Digg posts items on the main page by having its users vote on them, effectively using members as editors. Slashdot uses hired editors who have more stringent submission criteria. Because of this, Digg is more of a “cool links of the day” site than a news site. Personally, I like that, since I get my news along with the occasional cool flash game to waste half an hour on. This fact also means that digg has many more stories, typically 15-20 on the homepage per day (or a few hundreds, if you like to view everything everyone submits), whereas Slashdot has about 7.
2. Slashdot’s method is to have an entire forum on each post with a full-fledged moderation system (which works rather well), so you get a lot of insightful commentary along with the actual article, and that lasts (and is many times worth more) than the article. Digg’s commenting system is more of an afterthought since Digg is focused more on the articles (I think partly because there are so many of them every day) and half of the comments are people bitching/spamming their sites.
3. Digg’s voting system means that the news will be on the front page very quickly (almost as they happen), but they might also not be that checked for facts (some may argue that Slashdot’s posts aren’t checked for facts all that well either), so there might be rumours/falsehoods on it (the Gmail period mistake springs to mind, for one). Overall, I’ve found that the ratio in both sites is very good, so the conclusion here is that Digg is fast and Slashdot is good (again 70% because of the commenting system).
4. Some common ground here is that both sites have their corresponding “effects” (that’s when all the people on the sites cause half a datacenter to die and its owner to go bankrupt). I have been Dugg a couple of times (never Slashdotted, as I never have any breaking news to report) and I have to say that the Digg crowd is very well-behaved and polite, having left many helpful comments on my Dugg pages. I can’t speak of the Slashdot crowd by experience, but I think they’re a bit more “mischievous” in their reading.

This isn’t meant as a point-to-point comparison between the two sites, but rather to show that they are very different and should really not be compared. I read both sites every day and I don’t feel that they overlap in any way. Digg is a list of pages people have found interesting and want to share (with news items interspersed) which runs out when you have read all of them, and Slashdot is a list of a few news items that have much more to them than the article text, since each page’s comment section contains easily five times more useful information (and far more useless, but at least you get to not see those) and makes for a lot of interesting reading.

In conclusion, stop comparing the two sites. They most certainly won’t kill each other (at least not more than CNN.com will kill Something Awful). Read them both, they serve different purposes.