Frankie is right in saying that there is so much variation within breeds that you can't make a blanket statement about which will grow better.
Case in point: A friend purchased one of my former herd bulls, a polled Hereford, FGR Nevin Hudson N4. This friend, through the death of his wife's parents, had inherited a herd of about 30 purebred Charolais. In their case, their bull was several years old, but still in good shape, and threw good calves. However, they had to pull a few every year, and with replacement heifers being kept back, needed another bull. They went with this Hereford for a few reasons: Calving ease-he had a 70# actual BW, and we'd never pulled a calf sired by him. EPD was below breed average for that matter. My friend had always liked Herefords, and figured the temperament would fit in well with his cattle. They also knew through me of the bulls actual performance-740# weaning weight at 188 days on grass and milk only. Adjusted 205 was 804#.
When the next calf crop rolled around, there were two carryovers from the Charolais bull that were born a month before the group sired by the Hereford. When they sold at about 5-6 months old, the tan baldies had overtaken the straight Charolais in size and weight. The bonus was that calving trouble even in first time heifers was almost completely eliminated.
I know that heterosis has to be considered....but Mike, if the Herf was much of a dud at growth, the heterosis couldn't have made up the difference.
I've seldom seen a feed test where the herfs weren't the best convertors, as they were in the Kansas feedlot GOP (Genetic Outreach Program) the CSU studies, or most recently in the Harris Ranch study underway.