Which would be the better choice and why?

Buy the 80hp 912 Rotax and have the 104 hp Zipper upgrade installed, or just buying the 100 hp Rotax in the first place. Do Zipper engines make TBO and beyond without excessive wear?

In my experience, pushing a smaller power plant harder leads to a shorter life. I have also read on this forum that engine mods will void the warranty, so it seems like a better choice to go with an engine that produces the output you want rather than upgrading a smaller engine to the same power.

Steve