I just went thru extensive auditions of both those speakers and IMHO the Proac was to my ears a bit more musical. I also listened to many others and I would recommend listening to the Reference 3A decappo, better than both of the above in my opinion. If price is not an issue check out the Totem Manis, incredible sound.
Of your two choices I found the Proacs were a bit more interesting and a bit more refined, associated equipment was different but both SS. Either choice is splitting hairs really. But check out the Refs, thats what I ended up with, they are amazing.
Good listening