Hi Tans,
You may be better asking this question in the regular forum, pretty sure it will be seen by more people. I have the Starboard 12'6" and 11'2" and Naish 9'6". If you are after stability and flat water use the 12'6" is fantastic but much bigger and heavier than the 11'2". The three boards that you list in my opinion would not be as good as the 11'2" - my thoughts are 10x34, great stability but probably not much glide because of the width and relatively short length. 10'5" x 30 supposed to be fantastic all rounder with more wave orientation, similar shape to the 11'2" but will have less glide because it is shorter - great choice if you ever plan to get into the waves and easy to live with because of the length. 9'8" x 30 - too small for flat water and stability, really getting into serious wave territory.
The 11'2" is excellent for distance, not too long or heavy to live with and surfs really well. Look at the Starboard website www.star-board-sup.com and have a read of the forum. It would be worth asking the same question on the forum there, Wardog from surfingsports.com/ has a huge amount of experience fitting people up with the right board and he will probably respond.
Keep in mind I have never used either of the three boards you are asking about, so hey, what would I know! The Naish 11'4" is another great option
surfingsports.com/2008/08/new-naish-114-sup.asp read through the blog that this links to, there is a huge amount of information there about paddles and boards. Make sure you get a good paddle - absolutely crucial.
Phew - good luck!