Was that comparing c2 to game maker's HTML 5 or native export?
Aside from that, I'm afraid I don't understand the point of this thread either.
Comparing GML and c2 events is like comparing apples and oranges, some things might require less lines of code in either (for example, in c2, pathfinding requires barely any code at all).
You say the game runs better in game maker because you don't feel like coding it properly in construct? You'd have the same problem in game maker if you didn't code it right there, too. Shaders are quite intensive, of course they're going to require more work from the computer than just using another sprite for a reflection.
If you're putting in the effort to port a large game over, which you knew would be a large task, why are you not willing to put in a little more effort to fix something important that causes a performance hit? Sometimes the stuff in the "1%" is too important to skip. Also, not putting in the effort to design your code properly from the start can sometimes cause you to end up doing more work in the long run fixing your mistakes.
Also, where did someone confuse GML for c2 events? Apparently no one in this thread...