I wouldn't expect a huge difference, perhaps the KEF's bass might be a bit tighter (though your room might have more to do with this), and the Vandersteens might be a bit more coherent. IMHO, the Vandersteens are the better value. YMMV.
Vandersteen 3/3A vs KEF 107.2's
I was wondering if anyone can provide feedback as to the difference in sound and preferences between the Vandersteen 3's and KEF 107.2s speakers of the same era. Pricewise, the KEF 107.2's were about $1000 more. I own the 107.2's and am driving them with a McCormack DNA 1 Deluxe. I am a big fan of McCormack amps, probably because I havent owned anything better. I know Steve himself uses the Vandersteen 3A Signatures in his own reference setup. I'm curious if the older Vandersteen 3/3A's would sound better than my KEF 107.2's