Who's the better WB between Licht and Cuadrado depends on the opponent. Licht is better defensively, and Cuadrado is better on the ball and is a more attacking threat. When we play teams like Carpi, Cuadrado is the better choice. When we play against a team that is more of an attacking threat, Licht is the right choice.
It's not true that Cuadrado is completely useless with the ball now. He isn't in his brilliant dribbling form from the start of the season, but he still makes a few good plays per game.
But Allegri likes to pair an attacking WB with a more defensive one irrespective of the opponent. So, we'll continue to see Licht-A Sandro or Cuadrado-Evra.
Lichtsteiner is much better as a RB.
I think that's what I would have said before this season began. But going on match day form and seeing how each WB has been suited to the given systems (3-5-2/4-3-1-2) there are only two standout performers for mine. I would have thought Cuadrado would be better against compact defenses with his dribbling too but he hasn't shown that to be the case. He's almost better with one less man to take on. After one step-over/ankle breaker the second marker will seldom fall for the same trick which seems to be his only available dribble.
I get what you're saying. Licht is more defensively inclined so he is better at RB. But Licht is a brainier WB with an engine that is suited to the role. He makes up for the lack of raw skill and explosiveness (though he's not as shabby one on one as many presume) with smart movement and tireless running. In the 3-5-2 we play the ball in behind from the back much more than with a back four and his runs are either a great option or a great decoy. He plays to the system better than Cuadrado and that's a big reason why he's better. Not to mention how he wears his opponent down with his physicality. He's got that grinta and character that Cuadrado hasn't yet shown. To add, on this season alone, Licht even looks better at crossing. Bizarre. Compared to our last real right-winger, Camoranesi, Cuadrado is unfortunately looking like a clumsy pussy but I hope he can turn it around.
And as for your theory on Allegri's reasons for WB pairings, Alex Sandro is definitely not lacking in the defensive department. Don't let his ability going forward fool you. He is a LB after all, not a winger/forward like Cuadrado. He's just as good as Evra in defense, who has been out paced by his opponent a few times this season, showing his age a bit. Licht and Alex Sandro are beginning to start all the biggest games because they're higher in the pecking order (like Dybala - Mandzukic at the moment).
Evra and Cuadrado though, still very decent options and I'm glad to have them.