all the posts above have good things to say - i tink ya really gotta listen to these speakers, as they really are different, in many of the ways described, and ewe may really not like one or the other.
for me, personally, i've never liked any of the vandy's - they always sounded kinda lifeless, veiled, no soundstage to speak of. perhaps poor setup? dunno, i heard 'em in many different places, & they always struck me the same way.
proacs, on the other hand - well, i've never heard a proac i didn't like! ;~) great soundstage & very transparent. they never struck me as bright, yust accurate & musical. thiels are wery similar in these regards, to me, also. some folks say they're bright, i've never found that to be the case, & for a while, my system consisted of a pair of thiel 3.5's driven by an adcom gfa555, which *also* had a reputation of having a crispy hi-end.
don't purchase new, unless ya *know* it's what ya like,or yule risk losing a lot of money, having to sell & getting something else. that said, i'm saving for a new pair of newform research r645's - based solely upon what i've read of others' experiences! :>) i honestly believe that they will be nicer than anything i can get for their delivered-price of $2265, even if i buy used. *but*, they have a 30-day in-home trial, & if i don't like 'em, i'm only out shipping.
regards, doug