Lisa, I don't believe in "age appropriate", only body appropriate.
Age appropriate is mostly in the head. Only skirts higher than mid-thigh
(should be banned over 30) and stomach baring tops (should be banned over 45 except
near the beach).
The difference is in the cut, a size 9 women will have more muscles for
the same measures than a size 10, so the buttocks is higher, the thighs
leaner.
There is a difference in styles also, but its not that big.
Basically, if you an in shape women of 50, a 10 may not fit you well at all
because the cut is made for more fat which hangs differently on the body.