it depends on the type of riding you are going to be doing and some personal preference. The longer the board the faster it will go and the easier it will be to ride in pow, if you go for a shorter board you will not get as much speed but the board will be more maneuverable and easier to spin off of jumps. I have a few setups depending on the riding I am doing, my park board is a 155 my rail/street board is a 153 and my powder/back country board is a 158. You said you are 6'4 238 I would be looking at something around a 159 - 163 for yourself. I prefer shorter boards but I ride pretty much all park.