It can go either way really. The first release I ever put out was with a now dead net label called obscura records. Needless to say although it was cool to see something I made promoted by someone else, in the end it didn't help all that much . My current situation though is different. With my Collaboration Album FM-Possible being released on Noisechannel.org, I feel that Freque really cares about what he releases and will only take things of a certain quality. Then, he'll take it and make sure everything is tagged nicely, check for any spelling errors or song title inconsistencies, and generally make sure everything is nice and neat before he releases it. Then when he does, he promotes it well.
I think if you have the drive and will to self promote you should do it. However, if you want some help it's not a bad idea to seek out a net label. What I recommend doing is check out some net labels and see if the artists there interest you and generally make things you like. Basically it's about finding a label that fits you, and making sure that label hits your targeted listeners so that they in turn might promote you also .
Either way you go, make sure the album you make is your best and that you are enthusiastic about publishing it. It would also be good to have at least a small fan base before you do a release if at all possible. That way you at least already have some people looking to hear new music from you .
Well, that's my 2 cents . As limited as my experience is, I hope that helps you a little .