Of the two alternatives, self-publishing seems the best because in both instances the biggest hurdle is knowledge of marketing worth and methods. Only, by submitting it to the hard to reach and know gatekeepers(agents, editors etc.), it spares one a lot of effort and MAY produce much better results, which best results seem to be rarer so far in the self publication arena. Nowadays the great independent slush pile costs little and be made to order for digital readers and on demand printing. Even advertising has some very inexpensive alternatives. Reaching your best readers seems easier. Not surprisingly, standing out in the crowd and getting bucketfuls of royalties is probably harder in the democratic marketplace.
I'd rather get the work out there immediately with technical help and modest marketing in online places like Amazon's Create Space than play the long guessing games with those big firms who take the biggest cuts IF they decide you fit their company marketing needs- while you essentially remain totally unread and unmarketed, perhaps for years as the readers for agents and houses dwindle, the unsolicited manuscripts multiply. Every hurdle is a high one- and not often visible.
Book trailers on Youtube deepen the puzzle. Mostly they never include a single line of actual text, as good as the writing may actually be. They seem to make all the books seem like weak, cheap, movie script proposals. I suspect no one wants a mere proposal anymore in fiction unless you have a track record, a big name or non-fictional hardcore expertise. The expect the finished work if only for saving themselves time and risk. but they don't want to have to take the time to read them all either.