What are some alternatives?
When comparing PubMatic and AdSense, you can also consider the following products
Google Ad Manager - Grow revenue wherever your users are with an integrated ad management platform that surfaces insights for smarter business decisions.
AdRoll - AdRoll is a leader in retargeting display advertising. Draw the right people with the right strategies.
OpenX - Ad technology platform available as a hosted service or as an open source download.
AerServ - AerServ offers monetization solution for mobile publishers.
Epom Ad Server - An ad serving solution for publishers, advertisers, ad and affiliate networks
ONE by AOL - Ad Serving and Supply Side Platform (SSP)