TFW,
The industry requires a yardstick and hours is the simplest and cheapest - hence it is the common currency for aviation experience. Further, insurance companies will normally set a hours limit for command irrespective of individual airline requirements. In addition, individual airlines will set hours requirements as an auto filter for applications - this bar is movable depending on the 'market forces' in play at the time.
Aviation experience is a nebulous concept. However, I still contend that it is not hours that matter but the 'quality' of those hours and the experiences gained in them. If you have experienced 'fear' then the next time it is that much easier to overcome. If you have carried out a ditching in the Hudson, an engines out glide approach and landing in a heavy jet etc etc - these all increase one's experience exponentially.
So if I were a recruiter and I had two candidates of similar age and qualifications - one had 6000 hours / 3000 sectors on varied aircraft and the other training followed by mainly Ultra Long Haul flying who do you think I would prefer and who would you define as having more experience?
Now get on up to the 3F cos the inmates require massageee long time and need stress alleviation therapy
Happy Christmas.