Compare Different Vintages of Macs?

Maybe this? http://www.everymac.com

I used to own a 2011 MBA, currently have a 2013. There are some basic things to keep in mind when you compare it with newer versions. The 2011 MBA has slow USB 2.0 ports that limit the speed of an external drive to about 30MB/sec. In 2013 these were upgraded to USB 3.0. I get about 180MB/sec speed with inexpensive USB desktop drives on the 2013 MBA and the port is capable of much faster speeds than that.

The SD card slot is also limited to the speed of the slow USB 2.0 bus on the 2011 MBA.

In 2013 Apple also upgraded the wifi to the 802.11AC spec. This is also around 5 to 6 times faster than the wifi on your 2011 MBA. You might not notice much if any difference browsing the web, but if you use services on a local network, like a shared disk, it's a huge speed increase.

The SSD is also faster on the newer MBA. You might not especially notice this though.

Perhaps the biggest improvement is battery life that's almost twice as long, also starting in 2013. This is the result of using a CPU chip that's much more power efficient, and not the battery itself.

So you will notice a significant improvement over your 2011 MBA starting with the 2013 models. I would focus on these things and not CPU specs, which are really pretty similar and don't offer much reason to upgrade in and of themselves.