Originally Posted by Lemurion
As Xenophon suggested, submit one and write others. In most cases one's first novel isn't quite good enough to be published. Among other things they look for a 'breakout' novel first and so a novel that might be good enough for an established author may not quite reach the bar for a first novel. It's actually more likely that your first novel written will be your second or third published than your first published. (Needless to say this places a premium on writing MORE novels).
I've both managed a bookstore and worked for a publishing service (not a publisher, more like Lulu with hand-holding). If you self-publish you will only get into a small fraction of bookstores, (a subset of those you can physically visit) and almost all sales will come from someone who has heard of YOU before they became aware of your book. With a commercial publisher, most sales will come from people who discover the book before discovering you.
There's another catch to self-publishing: you have to work so hard to sell the books that you don't have time to write more, and that's where the focus of your writing career needs to be.
The only time self-publishing really makes sense is when you have an extremely specialized or geographically limited audience. It's great for local history books, and books on dealing with something that only affects a small segment of society.
This has really helped me to figure out what I want to do. I think for my first "publishable" novel (I've written others), I will try and go the traditional route. My first one is sort of teetering in between a large target audience and a more tightly focused one. With a few tweaks I think I can make it so that it's a little more niche and thus more likely to be picked up by a publisher in my niche field.
Thanks for all your help!