I have used quite a bit of Gelbvieh blood through the years, crossing red Gelbviehs with Red Angus and black ones with black Angus. They definitely add weaning weight. On the downside there are horns, calving problems, and disposition isn't always the best.
For the most trouble-free ranching, my loyalty would be with straight-bred Angus. There are virtually no calving problems. They are as in demand as any breed. There are no horns, and other problems such as bad udders, bad feet, prolapses, and bad eyes are very minimal. With the straight one breed system, it is always easy to keep your own replacements. The heifers not retained for replacements are often in high demand from other cattle producers who utilize cross-breeding in their own programs.
Angus are pretty labor un-intensive. For the ultimate in easy living ranching they can't be beat.