I disagree. I want the greens fast and firm. Super fast, super firm.
relative word.To some,11 is fast, other places that number is 14.
I like fast putts-not fast greens.
A fast green(14-15) is generally lacking in contour to be playable.
a green stimping at 8 can produce lightning fast putts if enough contour exists.
If all putts are fast, you're dealing with minimal contour, and minimal skill and judgement is required.
A 5% slope could present lightning fast putt downhill, that is barely nudged to go 30 feet, yet the same 30 footer might require a 3 fot long backswing coming back up that 55 slope.
If I had to pick fast OR firm, I'd take firm every time, and often the "fast" reduces the firm.