I used a set of Yana Shiki rotors on my Busa. I think it comes down to your budget. That's just what I could afford at the time. If you can't afford $576 (Galfer's MAP price) & $186 (Galfer's MAP price for rear on 08+) for a set of Galfers, then get YS. And get the look you prefer, Yana Shiki Rotors have a very unique look to them. You're building a custom bike, build it the way you want it. Are they junk? I dunno, they worked fine for me, and we have nothing but twisty roads in every direction out there. Likely I wouldn't notice if I tried. There's also EBC, Brembo, and Braking is a near copy of Galfer.
I'm a bit old-fashioned and would subscribe to the 'Get what you pay for rule'. But we've argued about Pazzo vs Chazzo for 10+ years on this forum. Do you want $150 Pazzo levers or a Chinese copy for $20.They look the same, or nearly the same. I'm still using Pazzo. That's just me.
Did they make me stop faster, not likely. If you want to improve the braking of your Hayabusa, change out the stock rubber lines (pure junk) to stainless steel. If you are a causal riders or commuter, you'll likely never notice the difference in lines. You need stainless steel when you go 20-30 minutes of sustained non-stop braking through a twisty section of road (which again is all we have out here). All my stock bikes got mushy after awhile and it's wildly annoying. Both my stock busa's did it, the Z1000's did it, the TL1000R is horrible with stock lines. And go to an aggressive pad like EBC Extreme Pro ($80/ front rotor). That's the biggest noticeable difference in my personal experience on multiple bikes.
It's your bike, if you like the look of the Yana Shiki Rotors, then get them. Personally, I love the look of the Galfer Wave Rotors, and yes you can buy cheap Chinese knockoffs of Galfer too. But that's me. I didn't keep the Yana Shiki Rotors on the bike very long. I'm building a custom bike and want it to look a certain way. And I wanted custom engraved/anodized rotors and you can only do that with Galfer. I've had Galfer Wave Rotors on 4 bikes in a row. But that's just me.