Most users most of the time won't notice the difference. But these are some the selling points that browsers have to work with. The fact that you don't notice the difference is possibly a good sign - competition has made it so that all major browsers have reasonable performance, from the point of view of the average user. Some might argue that wasn't the case 10 years ago, although there were many factors involved other than just the 'speed' of the browser.
For many users in many circumstances (by no means all) performance benchmarks are meaningless minutiae. When people ask me what laptop to buy, the features and hardware are usually pretty indistinguishable to them... if they've got a built in webcam and wirelss, they're pretty good to go... so I tell them to pay attention to things that may seem pointless, like which one looks nicer, which one has a better feeling keyboard... in many cases web browsers aren't any different.
But if you happen to know better for one reason or another, then you can already make your own choice