Why is 2017 MacBook air battery life so much better than 2014 MacBook pro's?
You have the 15" 2014 MBP, judging from the CPU speed. So you have an older CPU that uses more power; four times the number of pixels to push; and older battery tech. On the plus side, you have a larger capacity battery.

Your MBP requires an 85W charger, and the MBA uses a 45W charger. So that's indicative of power consumption.

Apple advertised the 2014 MBP at 8 hours of wireless web usage; the 2017 MBA is rated at 12 hours. So you should see 1.5x on the MBA.

I have the same model of MBP, and also recently got the battery replaced. I get about six hours using audio apps, Xcode, DTP stuff, etc.

The Device Name bq20z451 you quote is the model of the Battery Controller chip, rather than the serial of the battery itself, and is the same across a wide range of Macs with different battery characteristics. (Every battery also has a unique serial number.)