Caveat I've never flown Korean F. that said, the main difference between the two planes is that the A380 has the old F seat while the 748 has the the new suite. the new suite looks like the old one, but with a sliding door. So if that's not a big enticement I'd just pick the most convenient schedule. Both products look fantastic.
787-9 on new KLM biz class is a good score too. Otherwise, you could try to take a quick flight YYC-YVR and get on AF, but I don't know if they have the BEST seat on that route.