On form over the past 2 years then Vine+Narvaez>>Sivakov+Soler however as you rightly say they are all high quality riders that will give UAE the strongest team no matter which combination is selected.
Vine and Narvaez has a high ceiling but also been inconsistent and had problems. Crash prone.
Comparing them to Soler and Sivakov is wrong as they dont even have the same type of roles on the team or how they function in it. I would never exclude them two in favor of Vine and Narvaez.
Soler and Sivakov are two of the best doms in cycling. The disrespect and overlooking them has been strange in here. Been going on for too long. Two riders that should be automatic picks for the Tour for as long as they can be at current level, with probably Politt and Wellens as well.
The last three places... any combination of Almeida, Yates, Narvaez, Vine, McNulty, Del Toro... you cant really go wrong with.
I think it makes good sense in how they are setting up the team for both GTs, from what I see.