Well, basically it depends how much you want to spend… simply put you pay for marketing, while publicity is free! well free as far as you don’t give anyone any money, but of course it doesn’t just happen on it’s own, you’ve got to invest the time & effort, but it’s probably more fruitful than blanket marketing & advertising.
Invest your time building a dialogue with your audience, leverage social media sites & the web 2.0 revolution, find out what it is they want and give it to them. Don’t waste you time developing products then spend the rest of your time looking for an audience, invest your time in building your audience base, build a rapport with them, then develop products and services they want, stuff they will wax lyrical about to everyone else, thus in turn increasing your market share and exposure.
These early adopters become your publicity channel, continue creating products they want and they will continue spreading the message, focus on them, not the wider market, as they’re do your marketing for you, for free!