What kind of board to buy?

I'm a beginner, so bear with me.

I think I need a 143, but my ex thinks that is way too long for me. He's the pro, but he also only weighs 130 lbs, to my...well, a LOT more. I looked at the size guide on evogear.com and it sounds about right...and when I tried the shorter board I couldn't get up, like I could on the longer board. Since this would be my first board, I'm not against buying used and cheap. Also, it seems like I may be a slow learner, so I will probably use this board for a long time before moving up to something more rad.