Observation, I don’t have calipers to confirm anything:
The koncave seems a bit deeper than the centertrac. The centertrac pulls string away from the sides and into the middle region. The konkave is rounded, so string is forced/pulled to the center by the shape. The Crucial Groove seems about as deep as the centertrac, but it’s V-shaped to direct the string to the central groove.
The Terrapin X Wing Cut is merely a “center assist” concept. String layers aren’t forced to bunch up in the middle, yet for the most part, the string will be centered. I’ve heard the Wing Cut is like 3/100ths of an inch or some sort of really small number like that.
As far as what’s best or better, it really varies a lot. As you know, in regards to preferences, bearings also fall into that area as well. I personally find the Hiroyuki Suzuki signature yoyos work best with konkaves. Or, at least, I like them better that way. The Meteor and Speeder 2 come with flats, but I put konkaves in them and I like them better. The Phenom and Phenomizm come with konkaves. I haven’t put one in my Chaser yet.
My Crucial Half & Half seems to perform best with a Crucial Grooved bearing. Go figure. It came stock with a flat. The bearing is great, but it didn’t work best for me. Now that I put a grooved bearing in there, I like it a lot better. Because the ghost pads are thick, it keeps the string away from the pads and so it is less grabby.
There’s been discussions that bearings don’t make a difference. My thoughts, right or wrong, I feel that there’s a reason why some bearings are chosen to be installed into a yoyo. Of course, it’s nice we can swap out for what we might like. The guy I throw with on the weekends likes Crucial Grooved bearings. I tend to like either a stock-type bearing, but in some instances, I do like to make my own choices.
I’ve put Konkaves in other yoyos as well, but I just haven’t cared for it in those yoyos. But that’s just my experiences. I think we should all buy some bearing and experiment.