24bpp and 32bpp are very similar (Score 1)

There isn't really a difference between 24 bit colour and 32 bit colour. They both have 8 bits each of Red, Green, and Blue. In a 32-bit mode, the extra 8 bits are your alpha channel. If you have equal 24-bit and 32-bit acceleration, you get the same performance for less RAM. You might even get slightly higher performance because you blit one less byte per pixel to your frame buffer in 24-bit mode.