I think it was mentioned earlier in the thread but I'll repeat it...
Having a minimum of 1500hrs is a benefit to the industry due to the simple fact that 1500hr pilots will be a lot less willing to work for crap wages, vs 200hr noobs that just want a foot on the door and will whore themselves out.
As a result, when you hear the words "pilot shortage" here in the US, management will tearfully tell you it's due to the "ridiculous" 1500hr minimum. But the truth is that the shortage is due to less and less pilots willing to work for the crap wages those airlines start them at: A quick search will reveal that the US has thousands of ATP-qualified 1500hr pilots that are not working for airlines, so there is no shortage of them. They simply do not want to put up with the low starting wages.
As far as experience? I agree with the statement that hours do not necessarily equate to better performance... If those 1500hrs are all done flying C152s vs someone else flying night freight in a beat up twin, there's a huge difference. But overall, my opinion is that the 1500hr minimum serves as a decent experience "net" that gives us a good percentage of experience in the right seat...while not all 1500hr pilots will have 1500 quality hours, most will. (at least here in the US due to lots of different time building options.)
I have always had reservations about the MPL and low time cadets in the right seat...that's just me, maybe I'm old fashioned and believe 200hr cadets have no business piloting an airliner, but I'm a firm believer that airliner duty comes only after one pays their dues with experience and getting the crap scared out of them more than a few times while building time on their own... Transporting passengers in airliners is the pinnacle of the profession and should only come after a thorough seasoning. IMHO