Well, I knew it depended on your current armor and resistance. Asking my friend, he linked me the following table, which is mildly useful, but also extremely obvious and doesn't really give the answer I was looking for:
I had an idea though and I now present you with the RELATIVE usefulness of armor and resistance for increasing your TOTAL EFFECTIVE HEALTH: (It's very similarly formatted because I liked the original authors format, though my table kind of breaks the Conditional Formatting Color Scale feature.)
I have it saved in my public dropbox as well in case you want to edit it or play around with it yourself (EDIT: I updated the xlsx with a clvl parameter to adjust it to level 61-63 if you want, but it changes it very little so I'll just leave the original snapshot of the table as is.):
How to use and useful things to notice:
- If you had 7,000 armor and 500 resistance, it would take 13.89 Armor to increase your Effective Health as much as 1 Resistance. This means that +162 Armor is equal to 162/13.89= +11.6 Resistance, so 20 Resistance would in fact be more useful than 162 Armor.
- As a second example, say you have 800 Resistance and 5000 Armor, this gives you a relative value between Armor and Resistance of 6.32. So that means that 162 armor is equal to 162/6.32=25.6 Resistance. In this case, getting the 162 Armor would be more beneficial than 20 Resistance.
- The diagonal is all 10's because armors effectiveness falls off 10x faster than resistance, so if you have 10x the armor as resistance (X000 Armor and X00 Resistance, aka, the diagonal), it'll take exactly 10x the armor to match a given amount of resistance.
- The table is based off a 5% increase in effective health. This value was effective at keeping the largest and smallest numbers in the top right and bottom left cells reasonable. Changing this does alter the values in most the cells (the diagonals are always 10) but the changes were very small besides at the extremes, like at 14,000 Armor and 100 Resistance, which most people won't be at, and if you are, you already know which one is better.