I've read quite a few reviews on both games but I'm still unsure which one of the two I should buy (can't afford both games moneywise as well as timewise

).
I like both scenarios (realistic/futuristic), maybe the 40k setting a little bit better. I am more or less a SP player only, and I'v read that the Warhammer SP campaign is rather short...
What are your experiences with these two games and which one would you prefer/recommend?
(PS what I couldn't find out so far is whether there is in the WH40k

oW game some experience related thing like units getting better if they survive one map and are taken over to the next one, or new special attacks like in generals. Is there?)