Hi mate, you won't go wrong with either board, it's more of a case of finding one these days's. I was looking a Starboard a few months ago and none where on the ground. So when a Naish Nalu 10x29 became available at my L.B.S, I jumped in.
I was a little worried about the 29 inch width, I am around 6'3 95 kg's but have found the board to be fantastic. It's stable enough, sure I will take a dive every now and then. It only becomes a issue when the wind is up and water is moving everywhere.
The narrow width comes into its own when riding a wave, well worth the extra effort waiting out the back.
Go with the 29 mate, you will be very happy.
Steve.