I've got a recent XPS15 with an i7 that is way more efficient than a few years old T530 with an i5.
You want power efficiency when you don't load the computer much, while you might also want to be able to load it a lot to get e.g. fast builds. If you can get both (and now it seems that you can) it does not make sense to only get power efficiency while never allowing high perf for transient high loads (or even sustained load for when you are plugged in).
You want power efficiency when you don't load the computer much, while you might also want to be able to load it a lot to get e.g. fast builds. If you can get both (and now it seems that you can) it does not make sense to only get power efficiency while never allowing high perf for transient high loads (or even sustained load for when you are plugged in).