Err, not a fair comparison IMO -- EMSIA is high end 1/144 Gundam, Revoltech stuff aren't quite in that league. I think it's fairer to say Revoltech falls between MSIA and EMSIA.
The main point is that Revoltech joints hold poses better and longer than MSIA ABS joints. Unfortunately, the design of the joint receptacles often restrict the poses that can be done -- i.e., the "big nuts" syndrome, the limited shoulders, etc. etc. A MSIA/ EMSIA design with Revoltech joints would be interesting to see.
(Which leads me to a pet peeve. Where's my Revoltech joints set for customization? Kaiyodo is sitting on a gold mine there...)