If you look around the picture, outside of the hot spot, there is a noticeable difference in brightness in the spill, the Q5 being brigther. From some testing by users here, myself, etc, we have found there to be around 40 lumens more coming out of the Q5, compared to the Rebel. So those extra 40 lumens are giving you that slightly brighter spill, maybe a bit more in the hot spot, etc.
A Q2 with an OP would look slightly dimmer, but with a smooth the hot spot will look about the same.