Great thread. I frequently switch back and forth between surf craft. Sometimes all over the course of one day.
I am 6-2, 220# and like Old School above - have to beat waves into submission to catch them (that's a great line btw). The shorter you go the better you have to be at reading waves and picking your spot, as well as the pop up. I found that I suck at shortboard surfing and am passable on my longboard. Sure I can catch them if I am way inside using the curl to get that last push, but catching them otherwise on a shortboard is a chore (doesn't happen) and then unless the wave has some power- I sink. However, I ran across a McCoy Nugget on Craigslist and snapped it up. This thing has a big, wide, ass and it is so much more forgiving. Basically a lot of foam under your hips when laying down, and under your back foot when standing up. The difference is if you are slightly off the peak, you still get the benefit of getting the tail of the board high on the wave (doesn't sink) and can take off really easy.
Riding the board is different than a shortboard though. Because of the wide tail, there is sort of a pivot point right in front of the fins. If you don't get your foot on it, the thing goes really slow, but once you roll forward over it, the thing flies.