TwoSix
Everyone's literal second-favorite poster
I always found the DR change to be pretty minor. I used both types of DR, depending on what book I was sourcing the monster from. Sometimes I used them both in the same fight!And DR. 3.5 cut DR in half and got rid of specific +s needed to bypass it. That was pretty major. Spell duration changes were also pretty large.
The spell duration change was a decent sized change, for sure, but it was trivial to implement and didn't impact character building. At worst, it shifted the meta on the spells' overall utility.