UMMM...as far as I know there is no such thing as a two stage wakeboard (sorry) are you sure you don't mean continuous and three stage?? if thats the case three stage boards have a flat spot in the middle of them, the size of the flat spot can very generally boards with a larger flat spot go faster (because of the less of rocker) however this dose not apply to all three stage boards they can be slow too depending on how much it is bent, the other thing about three stage boards is that they tend to get a more abrupt straight up pop vs a continuous (no flat spot) which has a more fast smooth pop again can be faster or slower depending on the amount of rocker, when looking at specks anything less than 2.5 inches of rocker is considered pretty flat any thing above has more curve to it.
Note: continous boards tend to be faster than three stage boards with the same amount of rocker because of the smooth water flow across the bottom 'cause they have no flat spot
there are also other various rocker types off of those such as blended three stage which is like a three stage with some curve to it, subtle three stage, agressive three stage and agresive continuous (but as long as you know the two basic types: 3stage and continuous you should be ok)
landings also will very depending on rocker three stage will tend to have harder landings however if the botom of it has a spine or a v in it, it means the board will have softer landings than other three stage boards because that disperses that water on impact.
rocker type preferance verys per rider I myself prefer a three stage but I know there are plenty of people out there that disagree with me. (it also depends on the type of wake that you ride)
Now for sizes...longer boards tend to have softer landings but have more swing weight. what I would think would fit you would be some where between 135-140ish but there are always exceptions check this sites board buyer guide and the board wizard for good reconmendations for you to get you ideas
http://www.wakeworld.com/Wizard/Boards.asp (Message edited by wakegenie on February 03, 2007)