Talking about the Mark VI version of Ironman. Seems to me that the Warmachine armor has everything the Mark VI has plus a lot more. Now I am not talking about who is piloting the suits, just which suit is more powerful.
Now do you mean the mark 6 from the film, or the comics' mark VI (which I believe was an improved version of the grey armour)?
If it's the film version, I'd say the mark 6 - the basic frame is the same (robotics, repulsors, armour), but Tony's red and gold has a better power supply (synthesized element/vibranium vs. palladium arc reactor), and more high-tech after market additions, like his one-use arm lasers vs. the War Machine armour's conventional weaponry like the minigun and other projectile launchers - none of which are terribly useful against "hard" targets in the Marvel setting. Tony's armour is hit with weapons at least that powerful in the first film without significant damage (the fighter jets' machine guns & a tank artillery shell).
If it's the comics version, I'd give it to War Machine - his armour was based on a much more powerful model, as the comic's mark 6 was just an improved version of Tony's original armour, used after his bout with alcoholism.
Yeah, I meant the film version.