yahoo search marketing is same like the google adwords but it has a lot of diffrence than the google adwords. firt of all it is little bit cheaper than google adwords. it gives you $25 discount coupon for your registration about the yahoo search marketing and in addition to it there are several other benefits but keep in mind that only 4.8 % world traffic comes from the yahoo rest other come from other search engines ,particularly the google.
Its similar to google adwords.. In yahoo marketing competition will be low when comparing to google adwords.. mean time you are going to pay only if you get a visitor.. so no loss..
but the yahoo marketing has only 4.8 % worlds traffic and that too ,i am not sure all of them would be the buyer and apart of that if you are thinking about less competition ,i would like to tell you that less competition is due to less traffic. you have to be tough and go for the google adwords. and yes it is true you have to pay on every click for your ads. the rates also vary depending upon the per day CTR value of the keywords in both the PPC campaigns!
I don't think Yahoo is doing that well in Adwords and search marketing.. you would probably have better luck spending more time on other alternative sites 4.8% world traffic is low
There is a good video on Yahoo Search Marketing on YouTube called 'Getting set up with Yahoo Search Marketing PPC' Hope it helps