100% true.
With CFL's, as the (actual) wattage increases, the efficiency decreases.
Example:
The 23w ones are the most efficient I've found so far, at +/- 1600 lumens each.
The 45w ones are +/- 2600 lumens each. And so on.
So for roughly the same wattage, you'd get 3200 lumens by using 2 of...