I use digg, not reddit. I remember signing up on reddit, it was pathetic. couldn't find my way around it. Digg is much more easy to use(at least thats what i felt)
I think both reddit and Digg are very strong social bookmarking sites as long as you are professional and active on them.
I really like Digg and have built up some followers pretty quickly. I only post my articles and do enjoy the stuff the followers post that isn't theirs.Reddit was a bust for me. Got some traffic and first but then nothing.
Somehow happened that I use more Reddit, I like it. The only unclear thing is PR. Different resources indicate different PR of Reddit.