It is hard to resist comparing Glanbia PLC and Kerry Group. The two nutrition groups are among Ireland’s most successful indigenous companies. They both emerged from dairy farmers’ co-ops before turning into US-focused, listed international powerhouses. And they report annual results within a week of each other every spring. In their business models, they are increasingly convergent. As previously detailed, Glanbia, which released strong annual results this Wednesday, turned around its business after a few bad years by focusing on those areas where its capital returned the most profit: big brands like the sports supplements range Optimum Nutrition, and strong…