Why does MSAA cause my fps to drop but not SSAA?

Not sure why but whenever I select MSAA in p3dv5, my FPS drops way down. I tried using MSAA because I thought it would put less of a load on my GPU, but it seems that I can only get away with 4X SSAA in daytime and 2X SSAA during the nighttime. Being that MSAA is lower quality anti aliasing, I would think this would result in a performance increase. Just curious as to why this happens. I am using a GTX 1070.

Thanks