One major difference is the AWD system. The 01 had the viscous coupling that can wear out whereas the later models have the more favored Haldex system.
Besides that, the comparison is night and day.
Different engine, different steering, different brakes, suspension tuning, interior trim, exterior trim, wheels, and on and on.
They look about the same, that's about it. Every year brought significant improvements
I owned an 01 and have driven many (XC's) over the years of each model year including several 06's. When I tell you night and day it's an understatement.
The new cars feel and drive so much better, there's no comparison.
But your comment about body integrity, what's that supposed to mean, weird?