If you choose adwords your ads are displayed on websites related to your keywords and that's really ok because you get visitors that are really interested in your business! If i advertise on bux.to for example i think you get a lot of visitors that will stay 30 seconds on your website (in a frame) and than leave! What do you think?
I dont think then will stay longer.. Google is the number1 search engine , so it is more better if you will advertise on the no.1 for sure you will have lots of visitors then.
No doutb with google. it is the grandfather of all Ads network. Everything is better if i think. however, it is nice to advertise with adword and your visitors are really trustable.
Advertisement on PPC is also one of the most powerful interms of bringing traffic to the site. Although, it is risky coz' they have cost that you need to monitor. Specially if your site is involve in purchase or selling, co'z it is very visible to surfer and customers.
Don't go for those website. I tried it and it never works. It is good just to get you traffic, but it sends you uninterested visitors who visits your website because they are getting paid. So such sites are good for traffic, but not for business.