The first chart in the article explains the difference. It's not so much about being able to tell the difference, but how much it is protecting you in the background.
To be fair the only difference there seems to be from a future RC release of uBO that isn't even out yet, and also that has to do more with third-party tracking cookies more so than ad-blocking, so most users probably wouldn't notice it. It's not about speed, it's about the probability of detecting these CNAME cloaked tracking.
