I haven't tasted it yet, but
Graham's Good Keeper might taste better off the bat in Canada, since I think it may have been grown a lot there (granted, Canada is huge and probably has many different kinds of northern climates). It's on my to-grow list, but I'm not in Canada. Since I'm in the USA, I got my seeds from
here instead.
I hear Grot is also a long keeper. I haven't tried it.