Hi Stephan
Others will probably be more helpful as I haven't tried the Nalus. I have a 9'5 hokua for surfing and a very old 11ft beast of a thing that i use on a nearby lake and river.
So it's just my opinion, and not an expert one, but if i could have only one board it would be the 10'6.5. Like I said, I looked one over the other day and thought it looked like a good modern longboard design scaled up for SUP. The guy who'd surfed it that day said it had great glide.
Plus I'm a fan of DJ's video (which I recommend to you in case you haven't seen it):
www.seabreeze.com.au/forums/Stand-Up-Paddle/SUP/Surfing-with-JC/?SearchTerms=surfing+with+jcIf you do a search you will also see him on the 10'10 on flatwater and that wil give you a bit more info to work with.
(BTW If you ever want to post some pics or video footage of your local spots i reckon a lot of us would be interested.) In the meantime, good luck with the board choice.
Dave