A full shape allows off center strikes more powerful but it isn't possible with maximum edge size in lighter weights.
A concaved shape allows a maximum spine and maximum edge at a light weight. Off center strikes aren't as powerful as a full shape.
A semi-traditional shape is in between concaved and full and is balanced between big edges and good off center power.
A higher sweet spot allows for a more balance bat. The better the balance is the lighter is feels.
An oval handle is said to reduce the twist of a bat on off center strikes.
From October 1st the MCC has issued a new law that bats need to fit through a gauge. The specs are 40mm edges and 67mm spine (including 5mm camber). This will not effect most non-professional players right away.
(e.g. spine running through toe, special toe thickness, special shoulder thickness, copy of current/professional bat)