My concern on BGE's is that they seem to not really be big enough most of the time. A coworker recently made his second brisket and had to split the flat from the point to be able to fit inside. What size egg do you need to do a whole brisket?
Ceramics are usually more than capable to feed a backyard crowd.
On my Primo Junior with no extender grate.
15-17lb. whole packer brisket.
3 racks of ribs (4 is possible) with a rib rack.
2, 10lb. Pork butts (3-4 if creative).
2, Whole, bone-in legs of lamb.
Whole, bone-in beef shank (regardless of cooker I highly recommend. Very delicious!)
3 Lamb shoulders...
and that's just off the top of my head. I haven't done it, but interwebz pics of a Primo Junior cooking 2, 12lb whole turkeys are out there. While my Junior isn't the biggest ceramic, the oval shape adds a lot of capacity options as meat proteins tend to be oblong, not round.
When needing more grilling space I opt for a Kettle, but I assume most UDS owners do the same. A kettle also does double duty as a smoker.