Need advice on new board size

Alright first of all this is my first thread on these forums just like to say sup all, hope to get to know some of you better later.

Here is my situation; First of all I am in Michigan for a day under 3 weeks for work, I LIVE in Minnesota. I plan on ordering a Capita Stairmaster 2010, or a Horrorscope FK a few days before I leave to go home. I am stuck on what size though..

I am a tall and skinny guy sadly..
5' 10"
130 lbs.
I'm 19 and trying to gain weight as best as I can lol.
size 10 Burton boot.
'08 or '09 Burton Missions.
Will be riding mostly groomed, may take a few trips to Colorado, or Santa Fe, or Wyoming, but not this year I think.

So my friend who is just a bit taller and heavier then me urges me to get the 156.
Well I have been riding for about 9 years, freeride mostly some park the passed 3 years. Got really into it last year, did alright, but my board was just to stiff. It was mostly a mountain board it could have been a 157 or a 159 I can't remember right now.

Now I am upgrading still keeping my old board though of course for a back up, but it just won't do for jibbing.

What size do you all think I should get?

151 it is!