I find this kind of discussion both fascinating and inherently inconclusive at the same time; while I acknowledge that, at least in terms of pure tonnage, the smaller scale 'Mech that Mojo Amok provides a picture (very helpfully) of above is perhaps somewhat more realistic (ha ha), especially considering the sheer weight of the armour, I personally prefer the scale of the right-hand example. Considering the sheer volume of weapons (and ammo, even if we're only considering things like machine guns and their required materiel - a whole 200 rounds [which would take up a huge amount of space, considering that a "round" comprises the cannonade of gunfire that would occur in a ten second round], not to mention Auto Cannons, missiles - short and long range alike - would utilize), in addition to - as has been indicated - the volume that the cockpit would fill, considering that it has to be large enough to theoretically house the Pilot, and a passenger, for up to a week at a time - and food storage and washroom facilities - when working in a potentially hostile atmosphere or vacuum environment, we can't be looking at a space that's basically equivalent to what you see for a Formula 1 driver. Yeah, the theoretical Pilot and passenger won't be gettin' up and doing jogging rounds like Frank Poole in the Discovery in 2001: ASO, but they've got to have enough space to at least get up and move around a bit. The right-hand example fits this concept much better, from my perspective, and also...well, provides that intimidation factor that I think 'Mechs, and the interstellar empires (of varying sizes and capabilities, true) rely on to scare the crap out of resident populations that might otherwise be registering protest.