Are you looking for user/owner comments? It’s unclear. But I’ll go ahead and act on that assumption.
I don’t know if I have those exact models (515c are my others if memory serves), but I’ve been using Holosun sights for quite some time now in competition and for many thousands of rounds. All of the ones I use have the solar option. Based on my experience I would trust my life with them. In fact I have some on my more critical grab and go SHTF firearms.
The only misgiving I have is with the latest one I purchased which is an open model. It seems to me that if crud blocks the laser that projects the reticle the unit basically is kaput until it gets cleaned. I think I prefer the closed tube type that you’re looking at and which all of my others are. But so far no problems with it so I might be foreseeing problems that don’t exist. My one other open model is a Trijicon RM06 and I’ve never heard of that problem with it nor have I experienced it with that sight.
FWIW, I removed the kill flash filters from mine. They reduced image sharpness enough to bother me, and frankly, I don’t see them used for sniping, so anyone close enough to be bothered by it is also close enough to see me. If I need something like that I can cover it with my sniper veil and paying attention to the sun will greatly reduce any problem if in an ambush position. Others might see it differently and that’s cool. I’d like get their take on kill flash.