I don't think AR is necessarily as bad as it's made out to be for shorthaul travel -- it's in longhaul that it looks worst compared to other airlines. But that said, there is some risk of disruption due to strikes or who knows what -- hard to say how much risk, though usually strikes are announced with a bit of forewarning.

The Club Economy cabin isn't anything too exciting -- the upgrades to food and drink service are minimal if any -- but agree the space is nice if you're willing to pay for it. It also gives you an extra baggage allowance if that's something you value.

That said, how much time are you thinking is exactly the right amount? It's a tricky call because too early and the United check-in counter at EZE won't be open, but given the risk of delays on the incoming flight (not necessarily AR-specific delays, just the risk you'd have making a plan like this anywhere in the world) I'd ideally want about 4 hours, no less and maybe a bit more.