My experience is exactly to the contrary. Often ads are loaded from some horribly slow server and it slows down the browser which has to wait for them, reflowing the content after each one. Not to mention that ads often change when the page is reloaded, so they're not cache-friendly either.
Compared to downloading the ads, the overhead of running a blocker is negligible, no matter how fast your connection is.
I think it's the main reason Chrome (even with the ad blocker) actually feels slower on many sites compared to Firefox with AdBlock. It may win in terms of raw speed, but Firefox actually has to spend less effort loading the resources, which is a larger gain.
Compared to downloading the ads, the overhead of running a blocker is negligible, no matter how fast your connection is.
I think it's the main reason Chrome (even with the ad blocker) actually feels slower on many sites compared to Firefox with AdBlock. It may win in terms of raw speed, but Firefox actually has to spend less effort loading the resources, which is a larger gain.