Both are good for different reasons. To me, much of Burn sounds like Deep Purple and Whitesnake boinked each other and had a baby and this song in particular is probably the best example of that. (obviously, there are reasons for my terrible analogy). Burn was still a good album and probably the last good Purple album before the Perfect Strangers reunion in '84.
As cool as Spaced is, I have to go with Deep Purple in this matched up.