I haven't fully read through all of the above discussion above, but yes, Turkey Vulture (Northern) is the expected species in Ontario, and for all of Canada and the US. It's really just a preference thing, both for the reviewer and what they want to put on the filter and the observer and what they want to put on their list. There's tons of subspecies for nearly everything, some counties here have Morning Dove (mainland) and others on the filter as well, despite them not actually being identifiable as far as I know. There's been some debate among eBird reviewers, and I think there was talk of either making things like Turkey Vulture (Northern) the only filter option, or just doing away with it in all counties to make it less confusing. I typically just eBird the highest taxonomic level the filter lets me if it's something like that you can't tell apart. Things like Yellow-rumped & Palm Warblers, Whote-crowned Sparrows, Dark-eyed Juncos, Northern Flickers, Downy Woodpeckers, Green-winged Teal and countless others, I usually only eBird to subspecies level if I actually get a good enough look at them to be sure, as the other subsp of these species are very possible, and not to mention visually identifiable, in Ontario.
Basically a long way of saying, it's up to you what you want to eBird in terms of subspecies.