Ear rule here, but I don't show just do it for neatness putting on the bridle and halter. But when others here on the ponderosa showed they used the ear rule but would sometimes adjust to change the look of the neck a little bit.
Since you have a Quarter Horse the ear rule is probably too long. For them it is supposed to be pretty short. I'd clip about an inch and a half off. I have a Tennessee Walker and it's supposed to be much longer, so I clip around two and a half inches off. All depends on what the show people decide looks great for the decade!