The Akira was designed as a much more militaristic vessel than usual. Very similar in design to the Klingon Battlecruiser. With multiple topedeo launchers contained in a dedicated weapons pod and two launchers on the starboard and port sides of the saucer. Two sets of impulse engines, one set on the back and sides of the saucer and other set in the back of the catamarans. The secondary hull is directly attached under the saucer with the deflector. The catamarans, pylons, and engines give cover to the aft where shuttes and attack craft can safely enter.
The Titan was supposed to be a return to peaceful exploration. With teeth though. It was an enhanced science/combat hybrid to explore the Gamma Quadrant. A more traditional hull layout but with the engines blocking the secondary hull and a dedicated sensor pod above the saucer instead of being away on pylons on catamarans.
I know for myself I prefer the Luna Class as it better represents the ideals of the Federation but can more than defend itself and its interests. But the Akira is a kick ass battleship which is sometimes needed. They complement each other well.
The Titan was supposed to be a return to peaceful exploration. With teeth though. It was an enhanced science/combat hybrid to explore the Gamma Quadrant. A more traditional hull layout but with the engines blocking the secondary hull and a dedicated sensor pod above the saucer instead of being away on pylons on catamarans.
I know for myself I prefer the Luna Class as it better represents the ideals of the Federation but can more than defend itself and its interests. But the Akira is a kick ass battleship which is sometimes needed. They complement each other well.

