I have been reading up on mounting systems/methods for red dot sights on pistols. One school of thought holds that the multi-optic systems as the Glock MOS and S&W CORE are inferior to direct mounting, citing;

1) It's not as strong/robust.
2) It raises the height of the optic.

Obviously #2 is correct, while #1 "seems" logical, if just considering one less part.

But, does it really matter on the firing line? Just how important is height of the optic, in terms of mounting adaptor vs none? Are there reported (verified) failures of CORE/MOS mounts? So, is this issue:

True?
True, but inconsequential?
Just one one interweb talking point?

I prefer a lower dot just because I want it to automatically line up with where my Irons are or would be. I bought a EGW mount for a red dot on one of my 2011's... a couple of draws later, the slide was sent off to be milled for a lower mount.

The biggest issue i would think with the MOS/core style is an extra set of screws to come loose under the stress of recoil and loss of zero. I never had a problem with my G34 MOS that wasn't related to the dot itself (not the MOS mounting system), but that being said, I sold the MOS and am on the hunt for a milled slide to get the dot closer to the bore.

The height over bore issue is something that is easily dry fired out of being a problem. The biggest issue (and one the one that I have) is that going back and forth between irons and a dot is a lot easier if they are the same height.

I for one went totally to running a red dot on everything I own that's a pistol. The means to get there is both stuff you can buy off the shelf (MOS) and custom machined stuff for things like 226, vp9, etc. Sometimes a combination is needed for example to run an RMR on a 1911 I use the trijicon plate for that.
In the end I don't give a hoot about the very slight difference in height. Everything I've done has co witnessed irons and the minor difference in height does not bother me in the least.
Loose screws or a second set should not drive anyone's decision, that's fully preventable.
I've now tens of thousands of rounds in MOS glocks and there is nothing unreliable about the system.
FWIW,
j