Larian Studios Forums Divinity - Original Sin Divinity Original Sin - Beta Abilities - Speed

Constitution gives AP on each new turn and speed only on the first turn.

Con : hit point + AP per turn
Spe : Initiative + AP first turn (and max AP too it seems).

So speed is better only if the AP generate on the first turn is higher than the AP generate by constitution during all the battle.
And i find this is a brillant idea !