I personally love the Pro Penn Marathon Extra Duty balls. My high school uses them, and they generally retain their bounce for several months. Almost every other ball we've used usually dies within the month we get them.
For me, they also aren't too heavy or light, so hitting with them feels fine
I also liked using the can of Slazenger balls I bought. Only problem I had with them is the logo of the ball wears off, which kind of bothers me at times