I'm only still looking round right now and learning gradually as I'm looking to begin training next year hopefully, it does seem that doing a proper ATPL leaves more doors open for example if for whatever reason you became redundant you would not necessarily be able to go to another airline.
Unfortunately I can't post links yet to an article I read yesterday... but if you google search MPL vs ATPL theres a website called "pilot george" with some info - hopefully that will help you make a decision.