47" Octobox vs 30" x 60 Square Softbox

[rlconklin]

Greetings fellow camels, I'm in the process of setting up my home studio and am looking for suggestions. I pretty much decided that I'm going to go with 800w Alien Bee lights from Paul Bluff. Now for my question. For my main light, I'm not sure which soft box to buy. I've pretty much narrowed it down to the 47" octobox or the 30" x 60" square soft box. I plan on doing mainly portrait work (family portraits, senior portraits, and that type work) from head shots to full body shots. Which softbox would you recommend? Thanks for your input!

Also, can anyone explain the differences in lighting using a square vs octobox.