Without having seen or used one, I would assume they're not as fast, not as smooth, more expensive, more difficult to repair, heavier, and potentially bulkier.
If they use treads, they probably also have more traction on slippery surfaces. Having spent a lot of my life on snow, watching her go up that snowy slope made me cringe. I get she was with her husband and they recommended the buddy system, but I definitely would expect that thing doesn't just get stuck on soft snow/sand but also easily slides on harder snow and ice. Of course regular wheelchairs don't do any of that, still think this product is completely amazing. However if you lived somewhere where you were exposed to snow/ice a lot, one of the more expensive treaded options might be the right call for getting around in daily life.