I'm developing a middle level ad server and I use IHttpHandler for the ad handlers(ad handlers insert a few log, db connections and gets a string response at the end).
I would like to be sure which is lower than other and which is works with more performance. Or do you have any other recommendation?
A custom IHttpHandler is always going to be faster than MVC in terms of raw speed because of how early in the IIS Request Pipeline the IHttpHandler is invoked. However, depending one what you are doing MVC might be a lot more straightforward and easier to maintain for a negligible performance impact.
In order to offer a better recommendation it would be good to understand more about what you are doing.