I've not tried vinca on a hill, I have had it as a ground cover around foundation plantings. My gripe with vinca is that it doesn't get thick enough to keep out the grass and once grass gets in, it's impossible to get it out and keep it out. But then I'm not a consistent weeder so you might not have that problem.

I think I would try a varigated liriope or one of the varigated fescues (such as ÂGolden ToupeeÂ). Just some ideas.

I tried vinca in a small area (not a hill), but was not impressed. It does not choke out other weeds and it seems to hold onto fall leaves with a vengence. Hard to get them out without tearing at the vinca vines.

We have vinca on flat ground, on hillsides, and everywhere else and can't kill the stuff. Since you actually want vinca that should be encouraging news for you.

I have Vinca minor,solid green and a variegated form in my hosta garden,which goes up the hill beside my steps down into the garden. You're right about not being able to keep out grasses,but eventually,the vinca will do the job. About fall leaves covering the vinca,don't worry! The vinca will grow right up through the leaves in the spring and you won't even see them. Believe me,I live in the woods and there are plenty of trees! Just MHO. HF

Here is a pic to illustrate what I was talking about. The hostas grow right thru the vinca,and you can't see the leaves that fall in there.
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I have planted vinca illumination in a foundation area in our cold Canadian Rocky Mountain winter climate. I am very impressed. It actually stays green all year, despite our coldest -40 Celsius temperatures!

I would recommend it.

I am surprised at the comments about Vinca. I grew it around shrubs and it formed a very thick mat that would keep out all weeds.

However, in the first years while it is getting established it does need some help with weeding. Less each year and by the third year is is solid.

My Vinca illumination is growing very slowly. If you want a faster ground cover try the green version, and maybe grow illumination in another spot until you get enough.

I have vinca everywhere and have a love/hate relationship with it. I have to pull it from my shade bed on occasion. But do love the blooms in the spring. It does an excellent job on a pretty long and steep slope and has grown dense enough to keep the weeds out but it is pretty shaded too which helps. Plus, it has been there a long time. I have not tried the illumination so don't know how that fills in, maybe you could try mixing the green with the illumination.