I have to side with the OP's formula. Light heads transfer less energy to the ball, with a similar stroke. On fast greens, you don't have to worry about sledge hammering a putt past the hole due to a heavy head.
On slow greens, you have to really hit a light putter that can sometimes cause a player to change his stroke or get wristy. But, like the second poster also noted, what do I know? Been playing since '71 and building/re-building since '97.
I have learned that every player has a formula that works for them. Anyone who forces "standards" is shooting themselves in the foot, when people figure out how personalized putters should be.
LaMont in AZ