GSI all the way.
I found the only discernible differences between using my ps-270 and an hp-b+ were due to the closed handle and the price tag. The ps-270 felt more balanced to my grip , the needle chuck didnt rub my hand no matter how i was holding it, less junk got in the chuck area. The Iwata costs double.
Of course a c cup size does not bother me in the slightest but that might bother those who sight down the barrel.
Anyway I think as long as its quality it really comes down to personal preference.
That said Iwatas hold what like 70 percent of the market
Maybe 80 if you count some of the quality brushes that are the same designs.
When a design holds 80 percent of the market for 20 plus years its not because there are clearly better brushes out there. Especially when half of those people have tried and dumped H+S for one reason or another.