The Cougar X-Lite has 4400# axles and ST225/75R15-D tires, a much more substantial under-carriage than the Aerolite (3500# axles, ST205/75R15-C).
The Aerolite has a 19K furnace and no floor ducts so I don't know if the under-belly is effectively heated or not. The Cougar's furnace is 30K with a heated underbelly, including the dump valves (mostly).
I think the Aerolite bed is only a short king (74" long) and the Cougar queen is 80" (?)
The Aerolite roof is Al framed with hard foam insulation, dunno the R value. The Cougar's uses stamped steel trusses and fibreglass roof insulation with an R of 14.
I think the Cougar's back wall is "hung" not laminated. Dunno about the Aerolite. The Cougar has a full front cap, the Aerolite a partial cap.
Overall I prefer the Cougar 'cause of the beefier undercarriage and better heating. But I haven't seen either one.
Both of these have vaulted ceilings and large kitchen spaces. A similar floorplan in a longer trailer is the Laredo 240MK. There's also the Keystone Passport 23RB.
Once you narrow down your choices, I would go look closely at one, preferably without a salesman present, before making up your mind. I've always found something, good or bad, that no amount of internet shopping revealed.