Hexblade Options Question

So creating a 5th level Hexblade, single class, Variant Human and took the Pole Arm Master Feat for the extra attacks. Also took Agonizing Blast,  Devil's Sight, and Thirsting Blade as Invocations and of course the Darkness spell and Hex. Trying to decide whether to use the 4th Level Ability Score Improvement to bump CHR up to 18 or to take the Great Weapon Master Feat.

So, 2 questions:

1 - which is better, in the Forum's opinion, having an extra +1 to hit (both weapons and spells), an extra +1 to damage,(weapons and EB), and an extra  +1 to Spell Save DCs OR being able to use the -5 to hit +10 damage on potentially 4 attacks per round?

2 - is it worth taking the Devil's Sight/Darkness combo or a different Invocation (such as Eldritch Mind, Eldritch Smite, Improved Pact Weapon)? I have seen the DS/Darkness tactical combo  recommended many places but it seems it can create difficulties with the rest of the party, ie the Hexblade would need to move off at least 20 feet away from the group to use it without negatively impacting party members

Thoughts?

I will say darkness isn’t always very practical when your allies can’t see anything. Having said that, Improved Pact Weapon is useless once you get a magic weapon and eldritch smite’s spell slots are said to be better off used on normal spells. That ultimately leaves Eldritch Mind, which is normally obsolete if you take War Caster, but since you aren’t seeming to be taking it, I guess to me that would be the winner.

Keep in mind it can be a good idea to take Devil’s Sight even without the darkness spell just to ensure you are not holding the group back by not being able to see in the dark.

Thanks. Any thoughts on question 1?

Quote from Zeim59 >>

Thanks. Any thoughts on question 1?

 The answer to number 1 depends on a great many factors: Enemy AC, availablility of advantage on your attacks, etc. If you will be using Darkness/Devil's Sight to get advantage most of the time, Great Weapon Master will give you the best average damage regardless of any enemy AC you are likely to encounter at that level. Without advantage, you are probably better off getting our charisma modifier higher for the increased hit chance. At average-ish enemy AC's, the damage becomes about a wash when you factor in hit chance, but your damage will be much more reliable with a higher hit chance, with more frequent hits that are a little weaker.  

For the average character with a Greatsword at level 5, the math shakes out basically to this: without advantage on your attacks, GWM is worth it against enemy AC's of 14 or lower; with advantage, it is worth using at enemy AC's of about 17 or lower. 

As far as getting advantage goes, Darkness/Devil's Sight can be a great strategy to get advantage if you can either have a party build around the fact that you will be using it (by them getting Blindsight), or by your party letting you pick off one enemy at a time by yourself. It can also cause problems for the rest of the party if you use it at the wrong time, like against a solo boss where your party can't see you or the enemy. In the end, it is up to you to decide on what is the best choice for your character at your table.

Thanks. Keep in mind he has taken Pole Arm Master and so every time he hits with his primary attack he gets a second attack. The second attack is only d4, BUT with a +10 that gives (with the second set of attacks for Thirsting Blade) a potential +40 damage (on top of all his other damage plusses) if he uses GWM on top of PAM. Does that change the calculus?