As a professional genealogist, I have to be scrupulous about citing sources properly. If I find records via Ancestry for example, there is very clear information on the original source of the records and they even construct a suggested source citation. If you don't like the way they do this, then you can easily construct your own citations from the information given. Not so with Find My Past - there is nothing about the original provenance of the records found. They do boast elsewhere on their site about their "partners" of which FamilySearch (LDS) is one - would it kill them to say which record sets they have sourced from them?
Find My Past were right royally criticised for the appalling relaunch of their dumbed-down search screens a while ago, seemingly impervious to any criticism from their customers. It would seem to me that they are still letting their customers down by not allowing us to understand the true provenance of the records we are paying to search.
Actually, I think the explanation is simpler - they don't want to give clear information on the source of their records as that would allow us to more easily compare their offering with other (possibly free) sources of the SAME INFORMATION. To be fair to them, FMP does have a lot of very diverse record sets, some of which are unique, but I'm still not letting them off the hook when it comes to proper source citations. Granted, lots of people don't seem to bother with them (how many uncorroborated works of fictions have you found on-line passing themselves off as family trees?!), but for those of us who do, FMP is not giving us what we need. Proper source citations and better identification of underlying data sets are both on their Feedback board as user requests with a healthy number of votes for each, but I'm not encouraged at the "Started" label with no further information or time-scale indicated (another suggestion with the same label has a response from the support team saying that it won't be supported?!) Don't you think they ought to practice what they preach as this expert guide published on FindMyPast.com exhorts us all to do? If you care about this issue, get on their Feedback board and cast your votes too.
In the meantime, I'll have a go at picking through the various catalogues to see if I can come up with a helpful comparison but without proper source citation information from FMP, it may take a while - I'll have to compare start and end dates. Check back on the Dioceses and Diocesan Records page in the next few days and hopefully there will be a link to a comparison spreadsheet like those I've done for all the Church of Ireland parishes on the County pages.