What are the key benefits of both and does anyone use both styles?
I am big fan of shorter blade bats. CAs produced shorter blade bats long before they were popular and there was a lot of hoo-ha around "shorter blades". Now, shorter blades are the rage. The benefits of a short blade bat are bat speed, balance, and light pickup. I use TKs of Newbery Blitz shape which have shorter blades. They pick up light, pack more wood in the blade and swing a lot faster even when playing late shots.
It has been my position for quite some time now that bat sizes as we know are wrong! They were arbitrarily designed without any thought to function. Blade length should be adjusted according to the strength level of the player to product the optimal bat speed. Once that blade length is identified, the handle length should be customized for optimal balance and (again) bat speed. A true "custom bat" should never conform to these nonsensical SH, LH, Harrow, and other size standards! It should conform to produce certain output for the batter/user.