If I do a campaign with high stats, I just add a template or two to the creatures they encounter. A dire rat isnt a problem for a hero of equal level with 18 strength as his lowest stat, but what about a Psuedonatural Spellwarped Horrid Magebred Dire Rat? or in terms of villains, a Vampiric Lich Fey'ri.
The main reason you'd use high stats is if you've got a truly epic campaign planned, but It's just too deadly for the standard character. And unlike tomb of horrors, you actually want them to win with the same character. Personally its multiple elder evils; I want players to get creative. If you have Pandorym and Atrophus in the same campaign, see which of your players decides to try to harness the godkiller against the world eater. Or Ragnora/Atrophus; what happens when an endless generator of Life energy collides with a void of life energy?
On the topic of point buy; I like either way, but while I don't consider myself a min/maxer (That requires a competent understanding of how to play the game as a player >_<) I prefer Point-buy. Gives me a sense of control.