We recently had a customer ask about her west-facing yard. Here's what we said:
West facing side of house can still get a good amount of direct sunlight if there are not a lot of large canopy trees shading it out. The west side of our house is almost entirely shaded by a maple, cedar, and pine tree, so I would go with the Wood's Edge mix. If I cut all of those trees down I'd still have some young ash trees producing occasional shade, but would definitely get 6 hours of sunlight still so I'd go with the Door County Meadow mix or the Classic Prairie mix.
The number of sunlight hours and whether or not the soil is pretty usually pretty wet are the two things you want to keep in mind for picking a wildflower planting.