genetically though a seed grown plant should have the biggest cola
the primary branch is the one with the huge fan leaves and has the biggest bud
any clone can have a primary cola as well but this will always genetically be secondary growth unless the clone was made from the top of the seed grown plant which then will have the potential for a bigger cola than its mother
I think I have read that a long time ago anyway :-)
doesnt matter to me though I always top the plants and chuck the top