One piece bats are stiffer. There’s more feedback to the hands, so it’s best to use if you can square up the ball consistently. The stiffer handle transfers more energy to the ball, so it’s a great option for baseball guys who are transitioning to softball.
Two piece bats are far more customizable. There’s a lot of options for flex. Some of the variables are found in the construction of the handle; alloy or composite. There’s also additional variables based on the connection system used to attach the handle to the barrel. You’ll just have to swing them and find out what combinations work best for you.
Another variable worth considering is the knob. I’ve noticed the new stuff is coming with smaller knobs, including worth and Miken. There’s some brands like Warstic who skipped installing a knob. It just tapers and then swells at the hands. Seems like a weird place to add weight.
I suggest you don’t worry so much about what bat is “the best” and instead work on your swing. If your swing is good, it won’t matter what bat you use.
My favorite video I’ve seen on these forums is
@TWmccoy hitting 300’ bombs with a easton cyclone and a Easton hammer.