The various weapons in the game have a variety of stats, but I know that some of them (at least) are only useful to Shepard. For instance, weight. Squadmates are not at all effected by how much their weapons weigh.
What other statistics matter for squadmates though? For instance, adding a scope to a SMG or AR improves its accuracy bar in the weapon stats, but does that change how accurate your squadmates are with them? As they're computer controlled (or in one case, a computer), I doubt that they're really shooting wide or missing distant targets due to a lack of scope.
Squadmates have infinite ammo, so does it matter if their clip sizes or reserve ammo is larger? Do they depend on the "real" reload delay for a weapon, or do they spend a fixed amount of time in their reload animation regardless? Has anyone tested to confirm that damage upgrades actually mean something for them?