Family permit question

My cousin that lives in the uk is the son of the daughter of my father’s uncle, basically he is old but I am young, there’s a little inbred relations there (at the level of our grand-fathers) making us having the same family name (I personally am not an inbred child). basically my father and my cousin, allthough being a little bit far cousins, are very close friends, and me being my father’s son, my cousin wants to invite me to the UK.

This is an extended family member situation. I have all the papers proving that we’re related, but I ignore if going for a standard visitor Visa with a formal invitation would be more incentive vis-à-vis the fluency that the UK border control will provide me with on the “leave to enter”s situations, I.e. should I go for a family permit and have more freedom on my trips [going to the UK and leaving it would be more fluid(?)] Or do i do a standard visitor Visa of 6months, go on a 15 days trip, invalidate my visa when I return home, and ask for a new, longer Visa?