personally i'm looking for a few specific traits as far as how the plant grows along with the actual flower and potency.
I'm looking for the amount of stretch a plant has and the distance between each node. Also the amount of feeding needs to be taken into consideration, a few phenos from a strain can take on nutrients on completely different levels.
This doesn't necessarily mean that a heavier feeder will out grow or be more potent than a lighter feeder.
Also i veg my plants out from seed and flower them after taking clones from them. I've always done it this way but i know some that will keep the original seed plant as a mother and only flower out clones.