I’m certainly no string expert, but>
To me, it’s not just the thickness of the string, but the composition of the string.
Years ago, thick string was cotton or cotton/polyester and was usually finish wound around medium tension.
But now it’s waaaay different. The mixtures of string fiber types, makes for some pretty different performance characteristics.
And then throw in the variety of tight/loose recipes available.
Fat and fluffy and soft? Fat and fluffy and stiffer? Fat and fluffy with stretch or without ‘any’ stretch?
Fat, but wound tight and slippery. Some thick string is light for its thickness and some formulas are heavier feeling like neck chains.
Whips, lacerations and suicides can really fluctuate depending on the string formula as much or more than the thickness.
The thicker fluffier types that are lighter in weight from loose winding causing lack of cross section density, suck pretty bad outdoors if the wind is blowing at all.
Thicker, but tighter winds(for the thickness) stack up drag less with multi layers. As opposed to the thicker but fluffier, looser winds that really slow down spin time(but again, depending on the nylon, poly, Kevlar, whatever, makeup of the string). The slickness of some formulas seem to cancel a certain amount of drag simply by nature of their more slippery character.
I think I remember Zipline saying they have come up with 105 different formulas in an effort to see what does what.
There are obviously disadvantages to using thicker strings in general. But there are currently so many different yo-yo gap widths(in C size) and so many different response durometers of stickiness on pads. And several types, thicknesses and set depths of flow type response. Schmoove grooves… high walls, low walls, reverse cut, no walls, etc. it’s had to quantify exactly what disadvantages a thick string presents, because if so much variation in yo-yo design, gap width, response types, etc., can have dramatically different results.
Not even considering D size bearing yo-yos and responsive yo-yos.
No kidding.
PS…. One thing I personally don’t care for at all> thicker string that is wound in a way that the string won’t hold tension and either flattens out or coils up very quickly. No fan of those strings.