I'm not sure what it is about these two different swim settings, but I think it may be the one thing to separate the human race as we know it. In the future, people will be divided not by race, religion, or gender. No, we will be divided upon the style of swimming we prefer in Yooka-Laylee.
That being said, I'm with the majority in saying that the current swim setting feels clunky and overly complicated. All you need is a button to start swimming (with different speeds mapped to a different button, perhaps) and a direction to steer with the control stick. Shouldn't be too much more complicated than that.
With the current setup, the reason I think it's clunky is because I can't just press a button to swim, I have to think about exactly where I want to go in 3D space first: Up or down. Whereas if I'm swimming organically, I might want to swirl around a bit, oscillating between up and down at *free will*. And I think that's the point here. We want as much freedom of choice in this of where to go at any time... Leave the complex swimming controls to Mario Sunshine, which was easily the worst part of that game.