Remathilis
Legend
It removes an arms-race aspect from the game..
By having the DM win it from the get-go.
Here is my final piece of advice to anyone going down this road: if you are going to limit magic for your players, limit it for yourself. No archmages, only rare cultists or hedge-mages. Magical monsters are very rare and always have vunerlabilities to exploit. Your NPCs should reflect your PCs more often then not.
I say this because it is really easy to limit your PCs ability to affect things without magic and then use magic to shield your plots, NPCs and so on. I've seen it done too many times but more than one DM. So make sure you are playing but the same rules as your PCs, so to speak.
The best way to avoid an arms race is to agree on mutual disarmorment.