My experience to date is that the physical handling of an aircraft by low hour pilots is excellent. If the MPL system throws out pilots who have the same level of aircraft handling skills as my low houred colleagues, they will have done a good job. And I can see no reason as to they shouldn't have the same or better skills, because they will have spend more time in the sim. than the approved course chappies.
However, pilots with low hours have weaknesses in two areas. Firstly in operating an aircraft - basically due to a lack of experience. Whilst they can "pole" the aircraft to point X, they often don't consider whether they really should be going to point X. Secondly, and this is where the 1,500 hour pilot has an edge, they are often very immature and lack people skills (arrogant little sods, some of them). But overall, when you consider the overall skills of new First Officers, by the best are generally the current crop of ex-air force pilots. Not surprisingly, they move on to become good commanders as well.
But some of the worst pilots I have seen are the crusty old "Cold War" fast jet pilots. I found them lazy, supremely arrogant, slap-dash, egotistical and at times, bloody dangerous. I'm sure CRM was invented to deal with these obnoxious gits. I reckon they were passed out to be single-crew fast jet pilots because nobody would ever fly with them.
If the current crop of MPL pilots are exposed to realistic training scenarios and properly mentored throughout the training process, there is no reason why they can't qualify to become airline pilots and perform every bit as well (or better) as their colleagues who have been trained under the traditional system. The new system allows all of the rubbish regarding piston engines, the nuances of VFR nav, circuits, first solos, cross countries to be dumped. If you want to do that, fine but it hasn't got much to do with airline flying. The relevant bits will still be taught (and I think learnt more about VFR nav. when doing my line training in an F27).
Let's see the product before we trash it.