Personally, I cannot stress enough how subjective reticle choice is. I had a k624i for a short time, but for me I don't like the SKMR reticles. It's not enough info for me, mainly because I don't dial a lot during PRS matches. If that was for bench only use, where I was dialing all the time, it would have been fine. On the flip side, I shoot with several guys that swear by the SKMR reticles and refuse to run any reticle that is any busier so Kahles is their go-to.
Hardware-wise, they're both good. There's a definitive difference in turret feel, and Kahles has some of my favorite turrets on the market (2nd only to my ZCO but a former Kahles guy designed em so they're almost identical). I wouldn't sweat durability on either.
Before I dive into the following short book about reticles, again this is opinion, but the Kahles scopes are overpriced. The K624i certainly does not punch over $500 above a Razor G2 or a Mark 5 for instance. At $3500 for a 525 you'd be crazy to not just throw in a few hundo more for a ZCO at that point. With that said, used prices of both are more inline with actual value I'd say. K624s can be had for around $1800 and 525s around $2400-2500. They each fit much better there. Point being, don't let the Kahles price make you think they're somehow way better. I swear that if not for them owning the SKMR reticles their market share would be SUPER low, because that's really their claim to fame.
In my opinion, once you get up around the $2k price range, you start reticle hunting, at least for PRS because in this sport the reticle has to fit the shooter. Yes, different scopes have different feeling turrets, some locking, some capped, etc., but they all turn and in the $2k-ish price range they all (should) track. I've run a Razor G2 with an ebr-7c (wish it had a few more .2 mil hashes), a K624i with a SKMR3 (super clean, but not enough points of ref for me), a Mark5 HD with an H59 (a lot of info in there, and very busy, plus very thick at higher mag), Athlon Cronus g2 with APRS6 (very thin reticle, only really usable above 15x, not too busy), currently an ATACR with mil-xt (my favorite reticle to date) on one rifle, a ZCO 527 currently on another rifle with the MPCT3 reticle (also a big fan), and of course the XRS3 on an ELR build with the G4P reticle.
What gets very interesting as you deep dive into different xmas trees is how they organize their hashes. Many do .2 mil hashes and in some cases those .2 hashes all are the same size and position on the vert/horizontal line like the H59 and APRS6. When you're on the clock and holding into your reticle, you can find yourself counting hash marks to make sure you're on the correct hold. Where the mil-xt and MPCT3 differentiate in this respect is each .2 hash is somehow different than the one next to it. The mil-xt alternates on either side of the line they're on while the MPCT3 does different size hashes. Then you've got reticles that prefer .25 mil hashes (Leupold, Bushnell). Again, purely preference but I personally don't want that because my brain is so accustomed to .2s. Then you've got reticles that just give you .5 mil like Kahles. Specifically referring to the G4P reticle, for me anyway, it doesn't make a ton of sense with the different size hashes combined with dots and I would never run it on my PRS rigs. BUT, if you're coming from a G3 and always wanted just a few more points of reference, it may be a love affair. I have absolutely no issue with it on an ELR build because it gives some reference points without being too much and I'm dialing constantly.
Look at it this way, next to my ATACR 7-35 on my PRS rifle, I wouldn't spend the extra money on the ATACR to replace the Bushnell for ELR shooting. At the same time, I'd never run the G4P reticle on a PRS rig where I love the mil-xt. Again, reticles sometimes are king.
