It will depend on what you are looking for in a bat. The 2017 Easton Z-CORE Hybrid BBCOR Baseball Bat: BB17ZH will be a hybrid model with a composite handle and an alloy barrel. The benefit of this will be a decrease in vibrations felt on contact. The Cat 8 will be a one-piece alloy bat that will be stiffer on contact for maybe a slight overall increase in power.
The biggest reason you saw a performance difference is mostly likely just the heavier weight of the bat. If bat speed is equal, the heavier bat will always provide better power. Both this bat and the Marucci Cat 8 should be good performing models. Personally I might look at the Cat 8, simply because the Cat 7 was one of our best selling and best performing models. For cooler areas of the country, I would recommend getting an aluminum bat instead of a composite one, as they are generally more durable in cooler temperatures.
Based on his height, weight and age, we would recommend getting the 2017 Easton Z-CORE Hybrid BBCOR Baseball Bat: BB17ZH in a 32 inch model.