In the "old" ways of combat I agree Matt... The guys boarding would be the "marines" of old, but obviously those times have changed (somewhat) and Marines see service all over hell's half acre anymore. Definitely though I view the "Imp. Naval Trooper" as the Empire's actual Marine force, and their "Marines" pull double duty aboard ship more like the Marines of say the 19th or 18th centuries would have. To me though Stormtroopers transcend that.
I was speaking more or less with a wink when I brought this topic up... The uniform similarities, for seemingly no real reason, were why I mentioned it (between E3's Marine and E5's Snowies). I still view Stormtroopers as simply that... The Empire's "generic" Trooper for all seasons and climates used for security, spearheading attacks, and just generally getting the job done when you need it done... I sorta look at them as similar to the SS units of WW2, in that they were "prized" and used in all kinds of scenarios... They have their "deep cold" gear they throw on for missions like Hoth, a unique uniform that's not so much an homage to any past divisions of Clones but more just a functional design for the intended environment (not even so much the climate itself, but the whole environment of a world like Hoth).
The "regular" Stormie gear then for all the other environments (mostly anyway) with the modular packs to acompany them and to be adapted in an efficient manner with the right "additions" to it for the given environment. De-humidifiers for jungles, heaters for colder weather (but not arctic-like weather), AC/cooling units for warm/desert climates, and so on...
I was curious if anyone actually looked at E3 and it changed their view of the Hoth Stormtroopers then from E5 though... If they now were sort of looking at them as a continuation of the "Marines" then or what. I personally didn't, I just think they adapted their uniforms, and then that was found to be a good "style" for those deep cold conditions so the Empire carried that forward for their now bland/generic and completely anonymous army because it was functional (and of course they improved upon it some probably).
Weird things to think about... Goofy stuff.