I don't know much about Keele, but I had offers from both Sussex and Kent and they both wanted AAB. I got the feeling that the two of them were more or less the same standards wise. I went for Sussex because I liked the area as I personally love Brighton but I felt that Canterbury was a little dull and didn't really like it that much.
Just go for the one that you like the best, I don't think it matters much as they seem to have similar rankings from what I looked at when applying.