Your comment about vinca is interesting - I have read that elsewhere, but I had a large patch of vinca growing on another west-facing slope behind my house and it actually did best in the sunniest areas of the slope - there were a couple of spots along the edges of my yard where it got more shade and it was very slow to fill in there. This slope is closer to the street, though, and will get a lot more heat reflected off the pavement in summer, etc. I will check out the cotoneaster dammeri and creeping raspberry for sure!

Unless running water is a problem and therefore you need something with deeper roots, sedum kamtchaticum is what I would recommend.

Your instincts are right about creeping euonymus. It’s also unruly looking, sending up long stems in random directions, I’d go with the cotoneaster which arches downward and has elegant shiny green leaves.

Here is sedum kamtchaticum on my own west-facing slope. The brown parts you see are spent flower stalks. For a nice contrast, add some Orange Rocket barberry bushes.

Running water shouldn't be too much of a problem. In fact, my landscaper is pushing the euonymous because the slope will tend to be dry. The sedum could be a good option, although I really love the look of the creeping raspberry. I'm a bit nervous about trying it on such a large area though - I would hate to spend the time, money and effort getting it planted and established only to have a cold snap kill it off.

Could you trial it in a smaller area before committing to the entire slope? Just to see how well it might do? It really is a fabulous plant!

Just an FYI, but additional reading did indicate that although cold tolerant to zone 6, it is unlikely to be evergreen under those conditions and acts more like a dieback perennial.

IMO, in areas where this is sufficiently hardy, this is by far a more desirable groundcover than something like English ivy, as it shows NO signs of any invasive characteristics, does not climb trees, fences or other plants and forms a dense, thick mat unfriendly to most urban rodents. And it is deer resistant!

I may actually just cover the slope with cardboard and mulch next spring and let it sit while I figure out exactly what I want to do with it - I could try out a few different ground covers in smaller quantities that way to see what works best. I have also considered planting low-growing, spreading shrubs instead of a single ground cover (or in addition to a ground cover). I'll take some photos of the area and solicit some ideas. I have also thought about turning it into a rock garden with various sedums, creeping and alpine plants - that might be a bit more interesting than just a single ground cover.

At long last, I have photos! The larger area on the right with the false cypress is the part I'm talking about. The narrow bed on the left is less steep and though you can't see it in this photo, is planted with perennials and looks decent once things green up! I'm planning to add some small evergreen shrubs or perennials to that side this spring as well.

DH and I have been talking about various options all winter and he is in favor of trying to seed the area with creeping thyme rather than planting individual plants, which I agree feels like it could be a less labor-intensive solution (if it works). I have had good luck with creeping thyme elsewhere on the property so I'm thinking maybe worth a shot?