Steemit is always the busiest DApp:

https://www.stateofthedapps.com/dapps/steemit

So... from my rather limited experience, I would agree that Steem is undervalued.

On the ad revenue ...

I've been collecting BAT for a few months now. I know it's ETH, but it would be nice to be able to exchange that for STEEM... through some sort of tip jar.

Information of BAT:

https://publishers.basicattentiontoken.org/