The seats were designed with strong advice/feedback from orthopedic surgeons. They're supremely comfortable, but also a brilliant piece of engineering. They have a side impact airbag incorporated, and there's a pin that breaks if you get rear ended so the seat falls backwards. This is called WHIPS, or whiplash injury protection system, and it prevents - or at least greatly reduces - whiplash injury.
I haven't spent any seat time in an SPA XC60, but I've spent 131k miles in a 2012 P3 XC60 and it is the most comfortable car I've ever owned. That is coming from a rideshare driver. My primary income generation vehicle is a 2022 Toyota Sienna, with a 2010 preceding it. Both vans came along simply because my XC60 lacks one huge plus for any rideshare vehicle - a third row. Before I bought the first van, I never really appreciated how comfortable the Volvo's seat was. I could do a 10+ hour stint, get right out and be fine. I attributed it to being in my 20s and not having back problems. Even passengers fell asleep in the back seats quite often. Usually at least once a night I'd have to wake someone up. When the first van came along I noticed I was slightly stiffer and the seat materiel wasn't as breathable, causing persistent back sweat. With the 2022 now in the stable, that thing is awful! I have to stop every couple hours and walk laps around the van just because I hurt so much! The Volvo has been relegated to day job commuting and errands, but anytime I'm checking on my short term rental property an hour away, I'm taking the Volvo. Screw the van's hybrid fuel economy and adaptive cruise! The Volvo is faster, handles better, has a better stereo, and is so far and away more comfortable. It's 10 years older than the van with 231,000 miles (bought it with 100k) and is still a worlds better vehicle in a subjective sense. If only I'd been more persistent with a CPO XC90 instead of a stupid minivan....