Younger patrols can also look up to what the older ones are doing, such as having fancy meals at camp, and attempt to emulate. A running patrol competition system may not work well with horizontal patrols since there is such a difference in ability and size of the members. In a vertical system however, the PLs, who are older Scouts, may get really involved in a patrol competition and would work hard to harness and direct the energies of the younger Scouts in the patrol to compete. If well managed, this can be positive. A related issue is one of gender integration in patrols.
Some groups tend to divide patrols along gender lines.
I don't see a reason to do this, but I do see some disadvantages. Everyone in Scouting can benefit from a gender blind environment which forces them to see each other as people, not as boys and girls. Of course, local standards in most areas require separate tents for sleeping, but this should be the only separation. One final comment on patrol sizing. Don't make them too small.