I cycled across Canada last year. I had planned to take Hwy 13 in Saskatchewan, but part of it was under water, so I ended up taking Hwy 1. So I haven't cycled Hwy 13, but I have driven parts of it. It's very quiet, and more interesting than Hwy 1. Hwy 1 has a giant shoulder all the way from the the Alberta border to Regina.
From Regina I headed south to hook up with Hwy 2 in Manitoba, because I had heard bad things about Hwy 1 in Manitoba. Hwy 2 has absolutely no paved shoulder. The shoulder is thick, loose gravel, which is completely unrideable. There is lots of traffic, including lots of semis. However, the traffic is polite, and waits until it is safe to pass.
This year I drove out west. Hwy 1 in Manitoba has a good shoulder for most of it. There are sections without a shoulder, but it is a four lane, divided highway, so there should be plenty of room for vehicles to pass cyclists. If I were to do it again I would probably take Hwy 1.
East of Winnipeg I highly recommend Hwy 15/44. Hwy 44 is a nice, little, winding road through the forest with no traffic.