Almost impossible to quantify like that for me. The margins at test level are so tight that even tiny improvements in one area can lead to marked improvements on the scoreboard.
mm's difference between taking a try scoring pass and knocking on. Fractions of a second difference between delivering a try scoring pass and being intercepted etc...etc..
That said, England need to make a difference in quite a few areas in order to beat Wales, and in all honesty I don't see it happening.
We are the angry mob. We read the papers every day. We like who we like, we hate who we hate, but we're also easily swayed.