I usually have a few preferred routes for my normal routines. But, each time I go out, I usually vary the route a bit.

Thinking of different bike commutes over the years, some might have one primary route. Others I might have 2 primary routes.

I would never shy away from hills, and actually would enjoy adding a good hill in the middle of the commute (perhaps saving a mile or so overall distance, but really doing some climbing). I'd guess that I'd do 2/3 or 3/4 of the time over the hill, and the rest around the hill.