Personally, I prefer a dice roll. My experience with the point buy system is that the newbie (there's always one out there somewhere) is thoroughly confused and frustrated, ("Why can't I buy 18 for the same cost as 14?")and then there's the tendency for a party of adventurers who all have stats within 1 or 2 points of each other. That's probably due to a lack of experience and a little bit of "but they're all so gooooood,"
One thing that's definitely is not a good idea is 3d8. I did that once when I had only 3 players to give them a fighting chance... Then a 4th and 5th player showed up and we've got a party of 5th levels taking on ELs 9 and 10. Nasty and alot of work.( Oh... another young adult green dragon? But I've got shopping, you guys take care of it and call me when mama shows up.) I was about ready to have a secret demon summoner call forth a Ba'alor and accidently smudge the summoning circle just to end it all. Take my advice, if it ain't broke, don't fix it.
Oh and just in case you wanted to know the rules of that uber-elite farce, it was a) 3d8, reroll 1s & 2s (darn the co-DM) and a 24 gets rerolled and a free reroll of the lowest stat; b) scores capped at 22. c) scores over 20 go into a negative score adjustment. Maybe if I had a fixed stat roll instead of arrange to taste...