I don't know much about the 1440p route, but I'd say go for the greater HZ, you're going to get such a smooth performance with that rig. I got less than you and I get surprisingly really good.
+1 on this. Refresh rate is where it's at. This however has no basis whatsoever in ARMA as the likelihood of you seeing 60+ frames on
any server is nil. In other games however, it will be awesome. I yearn to race Assetto Corsa at 144 fps but the financial backing just isn't there yet. Playing around on a high refresh monitor is spooky at first. You just move the mouse around to enjoy the fluidity of it.
IMHO, if you're going higher than 1080p, 4k or nothing. Given the lack of good choices in panels and GPU's just now becoming available that can deliver 4k performance without taking out a second mortgage means 4k still may need to wait another year or so.