Why we should use Stumbleupon & Digg for Online promotion

How would you differentiate the users of Stumbleupon and Digg? I ask this because SU has been my top referral site in terms of traffic, although I don’t send any of my posts there. I sometimes send my posts to Digg, and I know it is a sin. However, I also submit other bloggers’ posts.

Can I conclude that Digg users prefer news posts, which is not my blog topic? Or basically, Digg users hate me because I submit my posts?

First of all, regarding the difference between Digg and StumbleUpon users, I would say that Digg users are relatively younger and more tech-savvy. The technology niche is undoubtedly the main one on Digg, and while there are many StumbleUpon users that are also tech fans, the overall population of its users is more heterogeneous (i.e. there are also many users that like videos, funny pictures, how-to guides and so on).

Keep in mind that this is what I have observed by using those services, and other people might disagree.
One essential difference between the two services, though, is how they work. Digg has an upcoming section on their website, where users are able to vote the stories up or down. The traffic that you would get from getting listed on the upcoming section alone, however, is not very big, because there are thousands of others being submitted every day.

Should your story receive enough votes to break to the front page (those days this happens at 150 diggs or so, but varies a lot), you would see a huge traffic spike, because virtually all Digg users keep an eye on the stories that go to the front page. It is not uncommon to receive over 100,000 visits in a single day from a Digg front page, in fact.

As you can see, Digg works under a “make or break” situation. Your content either gets enough traction to go popular and hit the front page, sending you a horde of traffic, or it doesn’t, in which case it will join the thousands of other stories that never get enough exposure or traffic.

StumbleUpon, on the other hand, works with a browser toolbar where its users vote the web pages that they see up or down. The higher the number of up votes, the more people will see the page via the Stumble toolbar. The difference here is that it is a continual process, and not a binary one. As a result, you will end up getting some traffic for most of your pages that end up on the StumbleUpon database, even if they don’t receive many up votes. Traffic spikes are also possible with StumbleUpon if a lot of people vote your story up in a short period of time.

Secondly, the StumbleUpon traffic is gradual and can last for a long time. If people keep giving your story or web page an up vote, it will keep showing to Stumble users, sometimes for months after it was first submitted.

On the second part of your question you asked: Can I conclude that Digg users prefer news posts, which is not my blog topic? 

News posts tend to perform better on Digg than on StumbleUpon, but I would not conclude that merely from the fact that your posts never got any traffic from Digg. As you can see from my explanation, the cause of that might be the fact that they never got enough traction (i.e. votes) to go forward. Should your blog keep growing its audience, one day it could starting seeing better results with Digg, even if your content style won’t change.

Then you ask said: Digg users hate me because I submit my posts?

I don’t think that is the case either. Digg users would hardly notice if you submit your own blog posts once in a while, especially if they never get close to becoming popular. This is only an issue if you end up submitting each and every new post your publish, regardless of their quality, and if you try to further manipulate the system by asking all your friends to Digg your story even if other Digg users won’t find it worth.