I personally am finding myself to prefer bats with very little to no concaving now. I recently started using a Newbery Mjolnir, and it has a big long middle with very thin edges and a traditional non concaved profile. The first thing my friend says is that I made a mistake and should have gotten a GT instead, as it has bigger edges and looks better. A week later, we were doing throw downs to play in the bat, and after trying the Newbery, he completely changed his opinion on it. Pretty much only one other bat I have used to date feels nicer driving off the front foot.
Ironically, despite me preferring bats with no concaving, that other bat is my Black Cat Custom made to the shape of a 2010 Distinction. The concaving is done though so that the edges are smaller than anything in the middle of the bat, and it is quite a steep concave in order to make the spine as big as possible to reward near enough any shot out of the middle. The spine height is really quite impressive even near the stickers. Despite being a student, I don't really like looking at the science side of things, and quite like to go for test runs and then base my opinion on that. Generally speaking though, I don't really like bats which have edges bigger than some parts of the middle, as it isn't the area where you are meant to hit the ball, and if there is any concaving, it has to be either very slight, or perform as well as my BC.