I would say Geriander as he wrote that the mass of the horse was important in the charging
I was mostly thinking about mounted units charging each other, not infantry. The horses themselves will collide and the lighter ones will be the ones that topple and throw their riders. If the lancers are only for chasing down fleeing enemies or charging badly organized infantry in the flank it wouldn’t matter as much. When European knights charge, It would be better to fall back and do the Parthian shot rather than collide head on with weaker armour and smaller horses.