It's getting almost comical the amount of customers who want the angle plug engines (we do sell both types) simply because they think the angled plug is a better engine with more power.
A centered spark plug will promote a more even burn, with the combustion force able to spread out evenly from the center outwards in all directions VS an angled plug that will heat up the side of the piston of which it's closest to.
Look at all Japanese and European two stroke engines, and see how the spark plug is positioned. Yup, you got it- it's in the center of the head standing straight up and down.
The angle plug design was only adapted to the bicycle engines for more clearance on smaller frames. It is a compromise, not an advancement in engine design as propagated by so many people.