According to the stage overview, there were six flat stages in the Tour, and there are nine in the Vuelta (including TT's).
I don't know why the Vuelta so often has a rather weak selection of sprinters. But it was a good thing for Magnus Cort some years ago, as it helped him to victories and more self-confidence.
Uh okay, so where was I wrong?
There are definitely not nine flat stages in the Vuelta...
Edit: Okay, I did forget Wednesday's stage to Cabo de Gata, sorry. But I still don't think the difference is that big.