Most competent recorder players also play the whistle. It isn't an either/or thing.

The big difference is value for money. Recorders are made in much larger numbers than whistles and there is far more historical experience at making good ones in a variety of types and sizes in industrial quantities. The result is that at every price point, you can get a much better recorder for the same money. The difference is extreme at the low end - to get a whistle with the accuracy of intonation and dynamic and tonal range of a basic school recorder like the transparent green Yamaha I often get photographed with, you'd have to spend more than ten times as much.

Conversely, the wonky upper octave, squeaks, extraneous noises, and random variations in intonation from nonexistent quality control that you get with a Generation make an unmistakable statement that you're playing a folk instrument. There are times when you actually want that.