I heard about this method in which you give the PCs one 18, one 16, one 14, one 12, one 10, and one 8 for their stats. What is the equivalent point buy for this? And how balanced do you think it would be?
It's 38 points. That's a wee bit powerful. I figure 28-30 points is about right for 4d6-six-times-drop-lowest when you chuck "hopeless" characters. I'm currently playing in a FR campaign in which we used 41 point buy. We're uber.
38 pts, as Leaping Shark said. It is definitely powerful but not particularly hard to balance. In both my campaigns, PCs get to divide 80 pts (not pt buy) among their six stats, which means some of them are around 40 pt buy (18, 16, 14, 14, 10, 8, for example), but I never have trouble challenging them with core material at CRs which shouldn't be a challenge for them. YMMV.
I play in two games that use a 40 point buy for stats. The PCs are pretty powerful but the GMs are good at making the encounters challenging. They use a lot of intrigue and puzzles where you can't simply use magic or brute force to win. In my game, I use a 36 point buy system. It's still pretty powerful but not as much as the other two games. The best part of a point buy system or in your case, specific stats, is that all the PCs end up balanced. If everyone has the same numbers to put into stats, then you don't have the problem with die rolling where one person rolls really well and another doesn't. I have found that it works out
better that way.
I use 38 point buy. I find that the power boost is basically offset by not insisting on a cleric-fighter-rogue-wizard party composition. Since I don't want to insist on the "classic four", I further find that this works well.
I'm really of the mind that getting an 18 simply costs too much and doesn't give you that much of a benefit. I like this 18-8 style ability scores and think it would be very balanced. If you are that concerned about the atrifically high point buy score simply knock the 18 to a second 16 and it's only 32 points. An 18 simply shouldn't be worth 16 points in point buy.
I play with the 32-point buy. It makes the players play heroes, not average joes, allows a viable choice with any possible class(es) and, in the end, does not really make encounters all that much easier, especially as the levels accrue - sure, an extra +1 here and there from higher than average stats (extra +1 over what they'd have had with fewer points to buy stats) makes a big difference at the first few levels, but once you're 15th level, with lots of bonuses from lots of sources - class levels, feats, equipment - those few extra pluses don't mean all that much.
So it does slightly increase survivability at lower levels - but that's a good thing if you want a long campaign.