I was thinking more about my comment and the only counter example I have is the Keg, which I believe does really well, so maybe it's hard to say, I still suspect it will not do well here.
That's a very interesting perspective comparing the areas
As we did the opposite i.e. we lived in Y&E and moved here ~ 5 years ago.
I really think it depends what you mean the "vibe isn't that great". In some ways I'd argue it's more vibrant than Y&E as strange as it sounds. I've found it always has more activity, and retail (of a certain type, I'll get to this in a minute) tends to do a lot better in NYCC when compared to Y&E where it struggles more, particularly once you venture a little north or south on Yonge.
Most nights you'll find NYCC pretty active all the way from Finch down to Sheppard, whereas in Y&E there's just a smaller pocket at the main intersection. I do have a theory behind that as well, I think the demographic at NYCC on the whole eats out a lot more than the demographic at Y&E, hence more activity and restaurants and the like tend to do better.
With that said diversity in retail is the major issue in NYCC I find. So if the dominant retail type is not your cup of tea that is a huge negative against NYCC without a doubt.
The other thing I appreciate about NYCC is the number of smaller parks / parkettes packed in the area (bounded by Doris and Becroft), there are just so many here. Whereas in Y&E there is a lot less green space in the immediate vicinity. Now in Y&E if you are willing to venture out a little further you are closer to a lot more major ravines and the like (belt line, ...).