Although my personal neuroses have staunchly led me down the traditional path so far, the short answer is I don't think either path is objectively better.
Traditional publishing is harder to break into. You have to please more people (agents and editors need to believe they can sell your book, and sometimes they're done with a genre that readers still want) and you have to deal with more rejection. It will stretch you though, and if you make it, the benefits are pretty huge: an agent to partner with, professional editing, cover design, print distribution, etc.
Self-publishing, obviously, is easy to get into. I could do it right now. But success is more difficult because you have to do it yourself. You have to edit it (I recommend paying someone). You have to get a cover (again: pay someone). You have to find your audience by yourself (and hope they're into self-published e-books). The benefits are freedom, speed, and control.
But in my opinion, the biggest danger in self-publishing is fooling yourself. Susan Quinn addresses this really well in her Seven Questions to Ask Before Self-Publishing. I've seen a few folks go to self-publishing before they were ready. Some had been rejected by traditional publishing and didn't take the hint. Some thought the praise of their writer friends meant that perfect strangers would feel the same way. Some believed the hype of the self-pubbing community and were surprised when they only sold 200 copies.
Which path you choose depends on a lot of things: your writing, your personality, the market. But very generally, my advice is don't self-publish your first book.
But do query it.
Most likely it will be rejected, but I think you can learn a lot by querying, without harming your reputation or your status as a debut author. (I should note that weak sales in self-pubbing might not be a lot of harm, but I personally think you can learn more from querying anyway, so why risk it? You can always self-publish it later).
But no matter which path you take, no matter how low the sales or how high the rejections, don't give up and don't stop writing. Not if this is what you want. There are a lot of ingredients for success, but I've become more and more convinced that the most important one is stubbornness.
What do you guys think? Is there a better path? Why?