which one ?

GTA. I hear its good.

i voted for GTA, but if you're such a Arma fan, maybe Arma 3 is the better choice for you.

keep in mind, that Arma 3 was discounted several times already. you shouldn't buy it for full price. i guess it won't take too long until it is 50% again.

GTA 5 of course :)

I've never played a GTA game. Of the two I hear the best things about GTAV though.

I don't like both so can't really advice anything xP
buy CS:GO?

Arma 3 is Awesome, but the Price is gonna go down, and there will be Sales with like 50% off soon enough.

GTA V isn't as good as it could've been, but the Price isn't going down anytime soon.

If it were me, I'd buy GTA V, and wait for a Sale on Arma 3.

GTA V at all costs!

Everyone is suggesting GTA V because it's the more popular of the two but considering how much you like Arma 2/OA, I think Arma 3 will be the best bang for your buck. That's assuming most of your playtime is in the base game or else the mods you did play are also available for Arma 3. As pointed out already, it has been on sale multiple times so wait for a good discount.

The games are too different for a direct comparison. It sounds like ARMA 3 will be the safer bet here, as you've already stated that you enjoy games like this.

Sorry for stalking, but according to your Steam profile you have 22 hours in Grand Theft Auto IV and 8 hours in Saints Row: The Third.
While I would get GTA5 for myself, my impression is that you may be much more happy with ARMA3

GTA V of course, It's best game ever.

GTA 5 = Fun

ArmA 3 = Immersive and suspenseful

Both good, I would go for GTA 5 if I had the choice again. Because my campaign in ArmA 3 is bugged so I cannot play it from the middle of the story on :(