> Software detection seems slow to me
It's faster than it looks like. Keep in mind that you don't draw that rotated thingy. So no ram -> vram delay.
However it's ofcorse slower than hitboxes. Btw don't forget that you can also just use hitboxes wich are a bit smaller than the sprites (own hitbox smaller/enemy hitbox bounding - in favor of the player).
Also those (vs alpha) checks can be optimised in several ways. Eg scanline-ish. But, as I already pointed out, it's slow and overrated. Really. Even the newest games doesn't use per pixel col. Just use in favor of the player collision detection and everything is ok