Falcon is a genuinely great friend - a ride-or-die if ever there was one. He's a road dog. He stood by Cap's side during Civil War and spat in the face of the government, even though he's a man who spent a good chunk of his life following orders passed down to him by his political superiors. His dedication to his buddies not only makes him a good friend, but it would - in theory - make him an excellent drinking partner.
Sturdy and dependable, he'd look out for you no matter what. He's not one of those guys who would just let bad s**t happen to you, and he wouldn't bail on you halfway through your misadventures. He'd stick it out with you like he did with Cap.
Sure, you could make a case that Bucky is an even better friend, but a drinking partner? Probably not. Sam has shown serious lightheartedness. Bucky, on the other hand, has a LOT of baggage, and with enough alcohol, a night with Bucky would probably get pretty dark. If we're talking pure, unadulterated fun and camaraderie, Sam's the guy.
In short: Sam would be the perfect wingman.
You get it. I'll see myself out.