In PVE sustain is not as big an issue, and more Magicka means more damage. 5/1/1 is most often the better approach. In PVP it's a trade off. At times less stats but better sustain wins out.
mag NB has siphoning attacks and very cheap swallow soul with HoT included so they anyway has good sustain so armor mix 5/1/1 is good. (mag NB with their sustain can even go tanky in 5 heavy to gap to enemy groups with sap essence and detonation up)
You can go either way tbh. These guys up top make good points and having the extra resources is a noticeable benefit in many cases. I do not utilize the undaunted passives for my magblade dps (in my tank spec I do use those passives). But I also don't use any form of recovery outside of siphoning attacks, relying solely on it and light armor passives for sustain. I feel this affords the luxury of sinking more into spell damage and max magicka, without having to take max stats that I don't really care about in my dps spec. The only reason you would want health as a dps is to avoid 1-shot mechanics, and stam is barely useful in pve. If you have to break free or dodge roll more than a couple times in an average dungeon or something, then you're standing in the bad mechanics, and it's not stamina that's causing you problems. My recovery is <900 and I never run out (the beauty of a magblade), but I also have 40k magicka and 4100 SD (self-buffed).