Polax52, it is an interesting debate because I agree with you to some extent and disagree to some extent. It depends where we are setting the volume control.
Although the previous reply was focused on cadets and low experience pilots, we (as a company) recruit a balanced portfolio of pilots from three sources. The cadets (low experience) come from full time integrated courses provided by one of the major FTO's. The other two sources are "experienced pilots." These are usually pilots with at least a few thousand hours of relevant airline experience. This group divides into two sub-groups. Experienced type rated pilots and experienced non-type rated pilots. Alongside the latter, the third group (also usually non-type rated) are the Military career changers.
It would be extremely rare to find "problem" pilots within any of these groups. All sources are well trained and the transition is invariably an easy one. Modern notech and CRM training tends to eliminate what used to be the occasional and very rare difficulty with the switch from a military background to a civilian training environment. Experienced pilots from other airlines are usually seeking personal career advancement or employment following redundancy for whatever reason. In any event the training background from the usual and preferred sources is (of course) invariably similar to our own.
However, experience does not automatically equate to safety as I am sure you would agree, and given that my next flight will be with a pilot from any of these backgrounds, I have no concerns on any score.
Turning that clock back 20 years you didn't find "self improvers" with 250 hours turning up on a Monday morning. Why? Simply because there weren't any. In those days the minimum (non-approved) hour requirement for a CPL (in the UK) was 700 hours. Even then, this was not a benchmark qualification for most airlines. Most "self improvers" reached this plateau and then used it to spring their way through G.A, air taxi, third and second tier airlines, to eventually get themselves the 2000-3000 hours that was often the first interview ticket for the Jet operators. Despite this experience, it has to be said that where "problems" did arise it was nearly always through this group. Given the often fractious and variable backgrounds that was perhaps not particularly surprising. Having said that, those "problem" cases probably averaged around 20% of which maybe 5% were beyond cost or time effective redemption.
Then of course there are a number of very proficient F/O's who do not make the grade deemed "command standard." Of course these become very experienced pilots, and very experienced F/O's. However does that "personal development" make them safer? Sometimes yes, and sometimes no! There can be occasions when it becomes problematic, and certainly it is something that you would want to try and avoid importing.
The group (and it is a very big group) who are left out of all of this, are the new 250 hour CPL holders, who thought the two thirds reduction in basic hours requirement, was their ticket to the stars. However improved the modular syllabus, it is often still a fractious, un-mentored and highly variable background. The CPL is now basically an "aerial work" licence in much the same way as it always has been in the USA and most other countries. It is the basic requirement to be a flying instructor, (previously a PPL would satisfy that requirement in the UK,) and embark on the stepping stone jobs. The reduction from 700 hours to 250 hours simply opened the floodgates to thousands and thousands of wannabes whilst at the same time many of the traditional "stepping stone" jobs started to disappear. For an airlines cadet programme they want what they perceive as the best, not least because they are not paying the cost of that initial training. Even if they were, they view these courses as surety for the standard of cadet that they want. They can monitor (and mentor in some cases) the entire basic training regime in a way no other system provides.