StumbleUpon's toolbar makes it super easy to submit and review your/others' pages. However Digg is more tech-centric, so you may fare better if you have a website in the technology niche.
When you lack the time to put effort into either sites, you sacrifice something in the process. Digg is well worth the traffic it brings for any category if on the front page, but to do so is very hard. You would have to friend a good amount of people on Digg. If you can find Power Users, you are well on your way. You have to show that you "care" about them as friends by commenting and digging their articles. Then you can unleash your articles and shout it to your friends. It is about a lot of luck and quality content. Stumble Upon on the other hand is very different. Yes, you can acquire friends and they can stumble your articles and websites faster, but most of the community will not stay on your site. They will most likely scan your article and leave. They seem to be picky about quality content and traffic rarely converts. You have two options: 1. Digg - Spend a lot of time building up friends and reputation among the Digg community to hope for your article to be on the front page. When it is, traffic will convert to subscribers and visitors. 2. Stumble Upon - Spend less time getting to know others and having people stumble your website, blog or article, but traffic rarely converts. Choose whatever you feel necessary, but remember the sacrifices involved.
I use stumbleupon I tried digg. Digg for me only gave me about 50 visits. While at stuble upon i got the highest amount of page views and that was in febuary at 51,000. I only have submitted 4 pages of 1 site and 1 page of my other site. Since then I get anywhere from 6,000 to 10,000 page views a day. With one site and only about 20 a aday with the other site. The pages now get submitted to stumbleupon by viewer's I have not submitted a page since febuary. The people said that they do not convert I make over a hundred a month.
Its both Good. But im preferably Good with dig. It gives me good traffic in my blog. While stumbleupon is not. I dont know why/.
Both are useful and good, but I'll go to stumble upon.. I got a good traffic of it better than digg. And it was more user friendly and easy access.
Estimated monthly traffic for Digg.com : around 12 millions unique Stumbleupon : around 6 millions Source : http://www.trafficestimate.com/
I'd say go with Reddit. It seems much easier to get noticed on. Perhaps that means theres less users though.
I like Digg better, but Digg results are fleeting, you basicly need to submit stuff to it every other day.
It depends on your website. For example, after some testing that I did, I found out that humor & entertainment sites get a lot of traffic from stumbleupon... This is because a lot of people that browse on SU are in fact, looking for fun On the other hand, digg is very good for technology sites in my opinion. Anyway, in the end they are both good for traffic if you know how to use them right. I suggest that you work with both
I will make life even more difficult, reddit is good too!! Seriously, open all three and just build one up faster.
Whichever you choose, beware of spamming you links in either. You can get banned easily for submitting each and every article you write to SU or Digg. In SU it's even worse - your domain gets blocked, so even other people can't submit your articles...