Pole-arm Master vs Unleash Incarnation (Echo Knight)

I’ve been playing an Ancestral Guardian Barbarian that took a dip in fighter (long story). I’ve decided is to go Echo Knight and wanted to buff my Constitution to make the most of Unleash Incarnation (an extra attack). However, I already have sentinel and have heard great things about taking pole-arm master with it. However, I’m already maxed out in strength and would be pumping dexterity beyond what is really necessary and would be sacrificing bumping up my Con with ASI. In other words, I really shouldn’t do both. (Should I?) It’s worth noting we’re at level 9 and aren’t suppose to come close to reaching level 20.

So, which one should I go with? The quick bump with Pole-arm Master, or the steady Con boost for Unleash Incarnation?

Polearm Master and Sentinel had a very nice synergy under the 2014 rules where the Reactive Strike from Polearm Master was an Opportunity Attack, so hitting an enemy that moves into your reach with a Reach weapon like a Glaive would cause the enemy's speed to drop to 0 while 10 feet away thanks to the Sentinel Feat. Under the 2024 rules, the Reactive Strike from PAM is no longer an Opportunity Attack, so this combo no longer works.

Even though the combo no longer works, Pole Arm Master is still a great feat, giving you a reliable attack with your bonus action and an increased chance of getting an extra attack with your reaction (which pairs nicely with Sentinel's Guardian feature). I would go this route first over boosting your Constitution, then bump your ability scores later.

Ok thanks. I guess I should have elaborated that I’m using 2024 tules but 2014 subclasses. My bad. At least this way is simpler and easier for me to understand.