Along with everything being said, Pixmap are quite fast when you need direct access to its memory buffer. There is way to draw a pixmap with OpenGL a bit faster than using DrawPixmap which does a YFlip internally thus allocating memory, copying lots of bytes, etc.
To sum it up: TImage vs TPixmap, it pretty much depends on what you intend to do.
To sum it up: TImage vs TPixmap, it pretty much depends on what you intend to do.