I think it's important to note that this is an online forum with various people often giving conflicting information - so I definitely agree with the above, you should take a lot of what you read with a pinch of salt.
Having said that, it is clear that the MPL has mixed reviews from aspiring and qualified pilots alike. My opinion, for what it's worth, the ATPL route is more desirable in terms of the amount of training and PIC hours, but going 'white tail' is arguably more risky due to the reduced job security. The MPL provides that job security, but reduces your starting salary - personally I think it's worth it! Especially with such a good company like Virgin Atlantic!
I understand that often the MPL is described as a licence which ties you to that airline as a First Officer with no possibilities to change airline or become a Captain. That quite simply is not true (from my research) - after 1500 hours an MPL will convert to an unfrozen ATPL which makes you just as qualified as those who follow the white tail route. I am willing to stand corrected on this, but I am pretty confident this is the case.