Ah ECBA? That stuff is ridiculous, with a plate that sits just off centre on your back making it impossible to fit a bergen comfortably! Give me Osprey any day.
But Osprey is bloody heavy. Can't carry that comfy began very far if your legs drop off with exhaustion. ECBA isnt as useless as you seem to think, works in the "conventional war" scenario.
You get used to Osprey very quickly because it fits to your body rather well. Depends what type of infantry you're serving with as to how effective ECBA is, Light role I'd rather have neither and exploit the additional mobility, armoured I'd rather have Osprey.
How good are the ballistic plates in the ECBA? because in thickness compared with the Osprey ones they see somewhat flimsy.