To work out which is better you have to do maths and work out what level your skill will be at for most of your playtime.
They also don't accomplish different goals. They both accomplish the goal of being particularly good at the same skill, and beating the age-based limits. They just differ in subtle ways that new players don't know about.
I meant as in "Major Magic Focus" and "Minor Magic Focus" being one skill.
I don't actually like the idea of the superspecialisation of affinity+puissant, but if it's going to be there, why shouldn't it just be "Majorly Puissant, +5 to the specified skill" rather than two essentially identical things that you stack?