Agnerod West vs Pledge of hands in a non-crit lightning caster

So i was going to finally start leveling my lightning caster CI berserker(Storm call/ball lightning, not entirely sure yet which one) and was 100% sure i would use a pledge of hands for the 7-link and use a dual curse setup of conductivity+ele weakness to get through resistances. While looking through other sources of penetration i found out that the Agnerod staffs give a freaking 20% lightning penetration. Due to the lowered curse effectiveness and the possibility of running into elemental equilibrium i thought about using the Agnerod West staff to make mapping/boss fights pretty smooth since you are at 60% penetration with 3% from skill tree, which is as good as it gets from what i researched.

So basically it comes down to whether the pseudo-7.5-link of Agnerod West beats the 7-link of pledge hands in boss fights/against tougher enemies. Trash should be fairly easy to take down either way.
Agnerod West's additional damage to lightning spells and +1 to lightning gems end up being ~25% more damage increase. That is, from what im roughly planning, about as much dmg increase as i would get from a max roll pledge of hands compared to a max roll agnerod west in terms of spell dmg differential(160%-50% = 90%, should be about 25%-30% more damage increase with what im roughly planning. Could end up being lower, but for now it is fair to assume it shouldnt be that big of a difference). So it pretty much comes down to level 30 spell echo + another gem against 20% lightning res + level 20 spell echo. But for that i might need some help.

Can the cast speed from level 30 spell echo compared to level 20 spell echo,a 10% cast speed increase, be treated as a 10% more modifier? Or how should i roughly evaluate it?

As for the penetration vs additional gem link: On a resistance capped monster(75% elemental resistance) and if i did 100 damage, i would deal:
65 damage with the pledge of hands and lightning pen gem(40% pen with skill tree)
85 damage with the Agnerod west and same additional penetration

which means i effectively get a more multiplier of ~30%, which is worse than a elemental focus gem with 49% more damage(which i was planning on using as the 7th link). Now at first glance there appears to be no reason to use the Agnerod west over the pledge of hands. Especially if i intend on using a double curse setup that reduces resistance further.
BUT the problem is maps like elemental equilibrium or bosses. So i need some help in that regard.

How much res do most red map bosses/guardians/shaper/uber atziri end up having? Are there any official values or estimates? I couldnt find anything.

Considering a 60% REDUCED curse effectiveness, i would end up having: 44(conductivity) + 44(Ele weakness 20q) * 1,2(curse on hit+skill tree) * 0,4 (60% Reduced curse effectiveness of bosses) = 42% resistance reduction. So if i can get them somewhat under capped resistances with reduction alone, i will probably end up shitting on agnerod west with a pledge of hands(since it will end up being a 20% more vs 49% more in the best case).

Now obviously i will be testing both of them in game on 5 links, but i have been wondering about which one is better for a first 6-link to get. If you guys see any flaws in what i roughly calculated in a few minutes, feel free to correct me. I am not 100% sure with all these mechanics in poe yet.
Looking at what i researched so far, i personally lean a bit more towards the agnerod west due to comfort and flexibility. But i have a feeling that Pledge beats it pretty hard outside of Elemental equilibrium map and elemental resistance maps on bosses.
for those of you who are not really interested in my thought process:

TL;DR: Does Agnerod West beat Pledge of hands in terms of damage in the endgame due to reduced curse effectiveness/high res of mobs and is hence the better 6 link for a non-crit lightning caster? Also is 42% resistance reduction enough to get bosses below capped resistances?

On a sidenote: If somebody knows a way to use EE with a lightning spell like storm call conveniently, feel free to suggest it. It would make the comparison pretty one-sided