I have had some success with both ends of the spectrum. Mostly onlinethese days. How about the rest of you. Please share which makes you more sales.
Online ads work well for online business, especially when selling virtual goods. Print ads may be good if you are selling something physical in a specific region + if you need to cover the segment of older/conservative people who read magazines more than the web. Also, as for print ads of today, I've found this post much interesting: http://www.creativebloq.com/inspiration/print-ads-1233780
In my experience print media has done well when mixed with online marketing. Really depends on what offer you are running.
Like Murfe said, it really depends on what you are selling. SEO service might not sell well with print ads, for example. For me, I am a fan of both advertising method, I am a little bit more inclined to online ads though.