is this the sort of thing you mean?
1,700 lumens @ 26 watts = 52.17 lumens per watt.
3,000 lumens @ 40 watts = 75 lumens per watt.
9,200 lumens @ 150 watts = 61.33 lumens per watt.
So basically the higher wattage each bulb is until 40 watts the better for getting the most out of cfl's
To be quite honest there isn't a massive difference I went from a CFL to HPS and it's not much more on the bill as I had so many CFL's running.