I am not sure about SP vs JP, but I have a TW and a US NS9900, both are 3U. I can tell from my personal experience that the US one feels heavier and stiffer than the TW. I don't know why. Others at my club also think the same when they hold the rackets. The difference could be well just the weight range of 3U (85-89g). The paint job looks the same to me.
That is simple thing, because the American more bigger and stronger than the Taiwanese. Also, Europe and America market, Yonex racquets grip only have G3 and G4. G5 and G6 are for Asia market.
I have owned 3 original Arc Z-Slash with 3 different codes (SP, TH and JP) and the difference I can tell is only based on the finishing/painting quality. I noticed that my TH coded was the lowest quality with the font spacing of the "Z-SLASH" emblem written on the 7 o'clock was not even. It looked like a "Z-SL ASH" instead. I have noticed that flaw when I bought the racket but the other piece left on the shop was even worse with some other flaws. The SP coded was better but still some flaws can be spotted under granny's style of inspection. When I looked at the racket from the cone straight to the frame, I noticed the wordings written on the shaft were slightly shifted (not geometrically straight on a line) and it has a couple of sharp-edge grommets on the frame. The JP coded so far has no finishing/paint job flaw under my naked eyes inspection... or maybe not yet ! Too bad I did not take any picture of those two TH and SP coded before I sold them but I personally believe that the JP coded has passed a higher standard of QC. In terms of material quality, weight, balance and durability, they are all pretty much the same and should be within the range of manufacturing tolerance.
Agreed with Cheung. It is all about sample size all the time when it comes to difference in products of the same product being sold at different nations. One might say that it is the same, one might say the contrary. The bigger your sample size is, the higher the probability that your hypothesis is correct, and vice versa.
well..looking at the uneven cross sections of racquets.. its definitely possible that there is even variation within a series itself.. and how yonex may do some selection. I would if i were them...
