im always amazed at how big the difference is between the a12,14 and 15, i have a decent a12gx setup and a mild a15, the a15 makes me feel like im driving a 6cyl compared to the a12, to get
the a12 to go fast I rev the crapper out of it and change gear as quick as possible, good for racing/rally
the a15 i dont take to max revs as it's not required and it pulls great after a nice smooth gear change, great for road driving
morale of the story.. what exactly are you looking to use the motor for???