IGI - to tick or not to tick?

Perhaps a good place to start would be their Research Wiki - at present the pages for each parish tell you what's available at other sites, but not in FamilySearch itself, which seems a bit odd... the high-level pages in the wiki suggest you search the FS Catalogue separately, but not all of the pages have a link to this so there's lots of faffing about involved. I suppose I should start adding in the links to the parishes I use, given it's a wiki, but it seems a fairly major oversight in the architecture of the pages to not have started with the information FamilySearch itself holds!

Even doing this, of course, would not be much help in identifying what's in each big grouped dataset like England Marriages.