Dean Smith, whom Shantnu Tiwari mentions in his/her answer, is an established writer with many books on the market published by established publishers. As a new writer, being published by a publishing house means that there was some selection process that filtered out the worst writers. As a reader, blindly grabbing a book from any of the big publishing houses means, that I will not be completely disappointed, even if it may not be my favourite book.
I travel a lot by train, and I often pick up books in train station book stores that I know nothing about, and it has always been an entertaining read.
Paying for and investing time in a self-published book is always a risk, and I have often been completely surprised by the total lack of storytelling ability, ideas and orthography. I only buy self-published books, if I know for sure that the book is good, and that is usually only the case with authors I know and like or if the reviews are overwhelmingly positive and written by reviewers I trust (such as in a newspaper of my choice).
I, personally, would always try publishing houses first, because they have the expertise to print the book well and market it, both of which I totally lack. Only if no-one wanted to publish it, would I self-publish.