Back to the original question, yes marbling is way overestimated in the "Quality eating experience". And yes final preparation is the key, right after aging. We spent four years using Pieds as the terminal cross. Huge mistake. They perform terribly in the feedlot for one thing. For the main reason, most housewives would buy the meat once and never again. The meat will rarely go choice, it is very lean. Therefore, you have to cook it like venison, hot and fast or it will dry out and be tough, the ordinary person would not know this and over cook the meat every time. You also have to let it rest quite a while after cooking, if you cut into it very soon all of the juice is on the plate and not in the meat. We could get by with the meat, we knew from experience, but some of the people that bought that meat were not satisfied.
About the cross breeding, we processed 96 steers 2 weeks ago, they are AN x GV. They were 61% choice, 1 YG 4, weighed 1326, but they yielded 66.5%. That (on a 1326 lb steer) is 3.5 to 4% higher than average, that is 46 lbs more meat per carcass. Last week we had another 80 done, 65% choice, no YG 4s, 1296 weight, 65.4% yield. You can't get me to go to straight bred anything now. Anybody want bulls that are mates to those steers? I have a few.