Cassiar is actually prettier. The Alaska highway is more "historic".
From a historic perspective go up the Alaska highway and down the coast
to Prince Rupert, then inland to the Prince George, pick up the trans
Canada highway through the mountains to Calgary (freakin GORGEOUS),
then on back home.

The coast is neat but nerve wracking flying over the water. There are
a couple of highways to the coast, though none of them go to Juneau
from generally the Whitehorse area. Its all flyable, given good
weather. File flight plans and bring a satellite phone (you can rent
them) for max safety.

If you get the Jepp Flight planner program, you can plan your flight
really well. Its all on there.

After my two trips, I bought floats for my Husky.

But no matter how you do it, it's gorgeous.