renewal changed a lot, some good some bad.
But the difference is quite big, to name a few,.
Pre-
Armor caps at 99 and the formula is pretty strong and easy to tank
Refine limit is 10
Gaining stats slowly increases in cost
No 3rd classes (duh)
A poring always give same exp
Stronger monsters are more rewarding
Skills only have variable cast time, Instant Cast is possible
10 level exp share
Renewal
Armor isn't Capped (i think that's a good thing), and is calculated much differently
Refine limit is 20
post 100 gaining stats requires much more stat points
3rd class skills which completely out preform most trans skills
larger level difference to a mob means less exp and drops up to 10 levels
stronger monsters are not as rewarding,on reason to kill them is to not get exp or drop penalties
cant get instant cast
15 level exp share
Edit:
II' sure i missed a few core things but think this covers most