Saying "tested to MIL-STD-810G" means very little. MIL-STD-810G is a giant document that establishes test PROCEDURE, and suggested test limits for many cases. You could use ESTI 300-019-2-3/-7, IEC 60068-XX or ISO procedures and still hit the same level of quality / robustness and in fact, the limits for many tests are nearly identical across these documents (free-fall drops, temp & humidity, thermal shock, etc). MIL-STD-810G is freely available online, and the document title is "DEPARTMENT OF DEFENSE TEST METHOD STANDARD - ENVIRONMENTAL ENGINEERING CONSIDERATIONS AND LABORATORY TESTS".
A big appeal of MIL-STD-810G is that it is FREE, whereas you have to pay for the ETSI, IEC and ISO specs. I've dealt with a lot of this on a daily basis at work for the better part of a decade, so take it from me that saying "MIL-STD-810G compliant" is mainly a marketing tactic, and if anything it means that MSI saved ~$1000 by not having to buy ETSI / IEC documents lol.
I really like MSI products because they tend to go where no one else thinks is worth it. Like taking a budget oriented processor socket and stuffing 2 full PCI-e x16 lanes on it and allowing the user to volt it up so far it will cause a fire.
I really like how MSI capacitors look. They are square shaped with beveled edges and look very durable. However, the square shape probably is not the best shape for a capacitor. A sphere or a cylinder would probably work more optimally. With that said, the space MSI's capacitors take on the board and there overall shape is very aesthetically pleasing and they look well built.
Personally, I don't think whatever grade capacitor matters since I have not had a capacitor failure in a decade.