Should use more than just trichomes... Some strains won't amber up at all.. then you sit there waiting while it over-ripens.
Trichomes definitely correlate to potency, but the anecdotes about them are not entirely accurate. The exact best point is based on people's unresolved feelings (eyesight etc) and not a matter of measured certainty.
Figure out what you prefer and be happy with that. Don'tn worry about pre-ordained anecdotal rules. Those are unresolved and unsubstantiated.
While i definitely consider state of trichomes, at this point i am more concerned about how long they ripen after the calyxes fully fatten up. If the trichomes don't show some amber within 7-10 days i'm not waiting for amber anymore...i can notice a poor taste from over-ripened buds.. they feel different when breaking it up, too. A little more brittle... older preflowers are hollow etc... unless it's naturally a long flower phase, hollow, brittle preflowers are a bad sign for my tastes.