ORIGINAL: PipeMajor
The LA40 is also heavier than the more powerful LA46 but neither has the power of a ball bearing 40/46. Why is it heavier? It has a thicker cylinder liner. Both have the same crankshaft (stroke) and case but the 46 has a larger bore (piston) which means the brass liner is thinner. Less weight, more power!
While you are quite correct about the weight, don't get too excited about it, as there is only 0.1 oz difference -- your airplane literally can't tell the difference. However, it certainly can tell the difference in power between the two.