Human eyes can only see 30 fps.
No but seriously, it all depends on your situation... you need to consider a few things:
What resolution?
What GPU do you have?
What games do you play besides Arma?
Gsync/freesync?
IPS or TN, or does it even matter to you?
If you have a gtx 1080 ti or higher, a 1440p gsync monitor might be worth it,but anything below that, there is honestly no point of a 1440p monitor over 60hz, even a 1080 is gonna struggle. if you have a pretty good card say 1070-1080 then i would go with a 1080p 144hz. Also, your preferred games, if youre only playing arma, then its completely useless to go 144 as the game runs like garbage. Now to get down to price, things like gsync and IPS are gonna increase the price a pretty significant amount, personally I think gsync is worth it but i couldnt give two shits about the IPS vs TN.