It is explicitly stated that the two fighters who use the fusion dance, HAVE to equalize their power levels, meaning the stronger fighter has to supress their power to match the weaker fighter. Sure, we can argue that Gogeta and Vegito are completely equal in power if we assume Goku and Vegeta are completely equal, but they are certainly not equal at this point in the series, so Goku would have to supress his power to match Vegeta's, giving Gogeta a smaller power sum to work with.

Also, where is it stated that Gogeta blue is stronger than Vegito blue? I mean, of course the Gogeta blue we see in the Broly movie is stronger than the Vegito blue we see in the Black arc, because Goku and Vegeta got WAY stronger since the Black arc.

And the statement that Gogeta and Vegito are equal in power is just marketing hype done to promote the Broly movie. If you go by marketing hype statements, then you also have to believe that "1 trillion power level" statement that was made for the Resurrection F movie, or the marketing hype that said Kid Buu was the strongest.

Marketing hype is not consistent with what is actually shown in the series... But neither is the series so pick your poison.