That’s kinda what I’ve been reading and my local gun store has been pushing the 507K. Let me ask this, is the HE507k green dot the same footprint?Well, I have zero experience with the Max 9, but a good amount with micro red dots. The Holosun 407K/507K would be my pick for the footprint the Max 9 uses. The Swampfox optics are garbage. Shield dots are expensive and not durable enough for me to want to use on a carry gun. I have seen and had problems with Shield dots. The Holosuns have good battery life, I like having the ability to manually adjust the brightness setting, you do not have to remove and then re-zero the optic to change the battery, they won't cost you an arm and a leg, and I haven't broken a Holosun micro-dot yet.
Hope that helps.
BTW, the Holosun 509T is on my RUGER 57 pistol and now I have a HOLOSUN AEMS on my RUGER PC chassis carbine where it is a perfect sight for that PCC class of guns.No more red DOTS for me. Since I bought a HOLOSUN 509T circle/dot I'll be buying CIRCLE dots from now on. HOLOSUN and SIG are making circle dots that I like and trust.
And I hope many more "red dot" manufacturers quit being cheap b______s and begin giving us all the option of a circle in their electro-optic sights. Leupold, Vortex, Bushnell, et al, are you LISTENING?