First of all, at this point you shouldn't be going for dhpt vertical.
But if you really want to, E1 always.
100 atk and 36 dmg% is nowhere near as good as 18 res pen & a skill point, if you want to play mblade then use a sustain that doesn't require pulling a mid flextape lc.
Dhpt vertical is honestly one of the simpler ones to follow in this game:
If you can get e2, get e2 before everything.
If you can't get e2, get s1. Do NOT waste your pulls on an e1 that is only marginally better than s1
If I see any of you with e1s0/e1s1 I am beating you up