Great feedback, thanks.
I began considering the UDS before starting the thread, but the footprint on a 55 gallon drum isn't small and it'd force a big rearrangement of garage stuff - also it'd be a big challenge to effectively use that since its got so much cooking space.
What's the footprint on the WSM? I'm not familiar with those smokers, but the grill that goes in a UDS is the same one out of the 22" Weber. Which means the drum is about 24" diameter I guess. I've got only one rack in mine and I don't feel like it's a lot of room at all. In fact, I'm considering adding another rack below the current one for more capacity. We're a family of three and most of the time it's plenty of room. But occasionally for a party or event where you want to do ribs, you'll want more room. Two big pork butts will feed a lot of people, and you'd be stuffing the drum pretty full to get two 9 or 10 pounders in there without touching the sides.
The great thing about the UDS is that it works equally as well if I put on one chicken, or a big brisket. Same fuel usage and stays super moist every time. That's my two cents.