the weight of the cyclist is placed further forward on a road bike,
but higher on a mountain bike. The difference in the angle from contact point to CG is negligible. Of course there is some variation - XC bikes are more tippy than DH bikes, USWB time trial bikes are front loaded, touring bikes with long front ends much less so, but these are all quite small differences, amounting to a variation in limiting deceleration of only about 10% either side of the mean. It is not possible to say that* all mountain bikes can stop quicker than all *road bikes. Frame size and rider weight disposition probably make more difference than generic bicycle type.
but higher on a mountain bike. The difference in the angle from contact point to CG is negligible. Of course there is some variation - XC bikes are more tippy than DH bikes, USWB time trial bikes are front loaded, touring bikes with long front ends much less so, but these are all quite small differences, amounting to a variation in limiting deceleration of only about 10% either side of the mean. It is not possible to say that* all mountain bikes can stop quicker than all *road bikes. Frame size and rider weight disposition probably make more difference than generic bicycle type.