Which is more important - a cover or the title?

I am in a quandary and I'm hoping that you might be able to help me. When I am about to start writing a new book I need to have the title in my head first, then the names of the characters, and only after that do I work out a rough outline of the story.
I'm absolutely certain that having the word duke in a Regency title definitely improves sales and also  using the word Christmas in a title does the same.
If you look at the four covers which ones do you think were the most successful? Did you choose because of the title or the cover?
It would seem that currently for a contemporary romance if the words, teashop, or any sort of shop, Cornish, little, girl, are included this also seems to improve its popularity. Indeed, the mainstream publisher I am now writing for is changing the series title of my World War II books to include the word girl. I was told that a girl's name plus the word war  no longer attracts readers.
The Reclusive Duke has been my most popular book so far. Then Christmas at Hartford Hall, then Lady Eleanor's Secret and last Victoria's War, Shadows.
I think the girl on Lady Eleanor looks too sad, but it fits the story perfectly. I love all the covers J D Smith does but for some reason some sell so much better than others.
If I changed the title of Victoria's War would it do better? Changed the cover? I doubt it.
I don't buy a book with the word shop in the title or if it has a pastel cover with hand drawn pictures. But then I don't buy books in first person as I can't read this. I just attempted to read a book by Nora Roberts, the characters and plot were excellent but she head hops so much it dragged me out of the story. Ten POV changes on one page!!
Personally it's the cover that I go for - I scarcely notice the title.
What about you? What makes you download a book?
Fenella J Miller