Hi Wingsward, welcome to PPRuNe. I'll leave others to comment on the marketing and price differences between schools but here is my perspective on the MPL.
It was first introduced by ICAO to address the argument that the ATPL courses produced people reasonably well qualified to fly light piston singles and twins but not adequately prepared to act as co-pilots in modern airliners. ICAO say: "The objective behind the Multi-crew Pilot Licence is to introduce an alternative pathway for ab-initio student pilots to achieve the necessary competencies to become highly effective, efficient, and safe operators of a modern commercial air transport category aeroplane through the successful completion of a seamless competency-based training programme leading to the acquisition of an aeroplane type rating, which satisfies the regulatory requirements to commence line operations indoctrination training with a specific airline." This is expanded by a useful IATA/IFALPA discussion
document which gives detailed definitions and summarises their view of the state of play.
The (original) key aims were competency based training, rather than the requirement to do a certain number of hours, concentration on the multi-crew environment and exposure to relevant new technology. Emphasis was also placed on the importance of aptitude testing.
When it was introduced the JAA, the precurser of EASA, IMHO failed at the first hurdle. We (Bristol Groundschool and Oxford at least) made representations to the JAA that they should not insist on a full 750 hour course for groundschool, nor insist on passing the existing ATPL exams but rather let us design theory courses that were relevant, were delivered throughout the training as flying experience increased and based on the concept of continuous internal testing. In that way the cadets would be taught basic met, for instance, in the very early stages and build up to microburst training and operational aspects in the sim phase. This is completely consistent with ICAO's expressed intentions (page 36 of the IATA document). The JAA, however, said no, and MPL candidates still have to do 750 hours of ground training and take the full ATPL exams. Commercial reasons make most ATOs teach them all this before they have even seen an aircraft, something else that is contrary to the original intentions.
The flying aspects of the course have, from an outsider's view, been more successful although plans to operate as multi crew in twins like the DA42 pretty much from the start have never gelled and MPL courses have tended to follow a more traditional single pilot path until phase 4, or occasionally phase 3 of the training.
From a commercial point of view, integrated ATOs realised early on that the MPL could cost less than an integrated ATPL to deliver, particularly if the economies of early ATPL theory, single engine pistons and fair weather bases (eg Arizona) were used. In my mind (and IATA's) these reduce the effectiveness of the original concept but they certainly add to the profit. The requirement to work with a specific airline in the later stages of the course also meant that candidates had to be effectively tied in to an airline, and this made the courses very marketable, as few 'tagged' places are available on normal integrated courses. From the airline's point of view the candidates are not only trained to their procedures, but are also effectively tied employees for longer than they otherwise would be, because a pilot holding an MPL license on the A319, for instance, cannot move as readily to that B737 job with BA as a CPL holder. The number of places on MPL courses are, however, usually small because airlines don't want to commit to large numbers a year plus in advance, so the ATOs tend to market the MPLs as a 'premium product' and offer standard 'untagged' integrated courses to those who are not selected.
The importance aptitude testing is also, in my view, overplayed by those with commercial interests. Yes, aptitude testing can filter out the really unsuitable but, for most pilots, it is more of an indicator whether training will be completed in the minimum time or a bit more. When an ATO has 4000 applicants and takes the top 15 you can bet they are going to be good. When the concept starts to fail is when the ATOs get greedy and lower the input standards, still no-one 'fails' the courses because they have already paid and the ATOs want to keep the money, and the integrated hold pools fill up with the 'not so goods'. The airline recruiters know when the standards are falling.
In summary, then, if you can get tagged on an MPL course at a respectable ATO like CAE, CTC or FTE you have done well and should (all things being equal) progress smoothly to airline employment. Don't expect the MPL to be the revolution it might have been, you will find it has been watered down by poor regulatory decisions and economics to effectively become a modified integrated course.