got mine for about 15 actually, and yeah 10% matters on this pretty much IMO due to the classes using it packing the worse ata in the game. My Fomar misses falz with the 3rd hit a good % of the time.
Gal Wind is more reliable IMO due to only using hard accuracy.
I can tell you from experience that a 40 hit Guardianna is worlds better than a 30 hit one. Like, you wouldn't believe. FOs need all the ATA they can. I still miss with 40 hit, but it's way more consistent than 30 hit. I recently switched from 35 to 40 hit and even there I can feel the difference.
You have to remember that the characters that mainly use this weapon have 163 and 170 maximum ATA respectively. Even 5 more hit matters. Guardianna is all about that last Spirit Hit.
Well fonewn can smack with it pretty well as well and he has 180 ata. So for that reason a 30 hit is ok at least. While I have issue hitting as fomar with the 30 on some targets, frozen foes can not dodge power from a 30 hit as well for example.
Should point out that 15-20 is an ok price for this.
But yeah that 40 matters a lot. Keep in mind that even with 40 hit this card has 5 less ata than a 50 hit charge raygun.