windward performance is all about L/D of rig and hull. If fact the sum of those drag angles (arctan(D/L)) is precisely your best pointing angle. That Alpha has no effective fin, it isn't going to weather well no matter how many hulls it has. Mark's point that there are some very un-weatherly monohulls is well taken, however those don't have a fancy website with unbelievable claims about speed.

As far as anecdotal stories go, I don't rely on them. I look only at published race results, these are hard to spin as anything other than what they are. The very best are races which are real time tracked by satellite. There is no wiggle room with the facts in that case. Take a look at the ARC tracker for example, many boats over many years. You can replay the event, multihulls and monohulls are easily recognized by their icon. You can see what specific boat it is by hovering over the icon. The better cats don't do badly, mixed in with the better monohulls. The fast racing monohulls are days ahead of the best cats. The slower cats are mixed in with the slower monohulls. The ARC is a downwind tradewind passage, this should favor the cats if any course does. Year after year, same story. This was true of the Caribbean 600 as well, which was also satellite tracked. Elapsed time in the Heineken regattas too. There are many years of results there, they tell a consistent story. I would love to see some published results over a few years of a well attended race that showed cruising cats consistently beating same sized monohulls. This was the subject of a long knock-down-dragout over on SA, no such results could be found.

Even in extreme racing machines the differences aren't great. Take a look at the TJV race tracker. The Mod 50 tris and the IMOCA monos are fairly close, any upwind and the monos get ahead, the tris do pull away a bit once in the downwind trades.

http://www.worldcruising.com/arc/eventfleetviewer.aspx
http://www.heinekenregatta.com/Regatta/Results.aspx
http://tracking.transat-jacques-vabre.com/fr/