The Party has more "headroom" between the charcoal basket and the water pan then the Fatboy. I had a charcoal basket made for my Party, it was about 9" inches tall, and fit inside the Party charcoal tray. I also have a Fatboy, that I use with just the stock charcoal tray. The span between the Fatboy charcoal basket and water pan is considerably less than that of the Party. However, the Fatboy charcoal pan is much larger than that of the Party. I will likely have a charcoal basket made for the Fatboy as well, but really have not yet put much though into the dimensions. Having owned and cooked on both cookers, I really have not noticed much difference between the taste or efficiency of the two cookers, although you would expect the 2" insulation on the Fatboy to translate to less fuel useage, especially in cold or windy conditions. The Fatboy was designed to cook and entire KCBS contest on one cooker. I have cooked entire contests on my Party, with a BWS Chubby as insurance. Both are fine cookers, and will likely suit your needs. It is hard to quantify, but for my money, the Fatboy is somehow a more "serious" cooker, more well suited to KCBS contests. The lightweight of the Party is nice, but since I only need to load it for travel a handfull of times each year, I am willing to overlook the extra pounds of the Fatboy. I think you will be happy with either choice, and can make excellent food on either. If you have additional questions, I'd be happy to help.
Jellyroll Jones BBQ - Madison, Wi