So there are two (at least, that I know of) plugins for displaying ads:
https://meta.discourse.org/t/google-adsense-plugin/11763
Has anyone used both, and can compare? In particular,
I used both…
Both are awesome 
The official has got more options for ads, the @michaeld’s one is only for adsense.
The official do not break Discourse.
I do not use Michael’s now. But do not break my discourse either.
For ad placement, read the info for each plugin, both are great.
I don’t know about that. Michael’s plugin doesn’t support responsive ads and can’t show ads only on topics.
The official plugin doesn’t support responsive ads either, and can’t support displaying ads only to anonymous users, unless you hack the CSS to hide the ad (which means logged in users still waste time and bandwidth downloading the ad).
this issue still exist?
I don’t think this is true any more @neil?
The official plugin supports AdSense responsive ads. To only show ads to anonymous, you can add trust level 0 (i.e. everyone) to the setting “no ads for group”.