It was a year and a half ago, so I don't know how well my memory can be trusted with the details (as I was on vacation in AZ when I heard both and did not take notes)...
But with that said... I remember listening first to a pair of McIntosh XT-28s that I just was truly impressed by. Then right afterwards in the same room, the dealer setup the MS5s and played the same tracks from "Allison Krauss Live" and I remember commenting that the MS5s sounded flat compared to the McIntoshes by a long stretch. Pretty much I felt the female vocals did not sound right to my ears on the MS5s... I also was not particularly impressed with the bass extension (although it could have been the music played on them).
Next up was the Helicon 800s, and a saxiphone track played that was absolutely phenominal... I thought the Helicons were the next step up in the Dali line until the dealer informed me of the various price tags of the speakers I had heard so far. When I heard the price of the 800s, I thought that they were a great value for the money, whereas the MS5s just had me shaking my head. I finally rounded out the session hearing the Megalines that were superb, but way out of my price range. Still it was worth a listen, as they were remarkable speakers, IMO. All electronics were solid state top-of-the-line McIntosh solid state, BTW.
Bottom line is the Helicon 800s drew me into the music, and really had me tapping my feet, enjoying what I was hearing... the MS5s left me cold, just not interesting me. *Maybe* they were more accurate... If so, I'll take "less accurate" in this instance any day, as it sounded more like I would expect at a live performance. Oh, and they also did the Allison Krauss album better too...
---Dave