Hey,
IMO weapon comparison is a bit akward. Type X weapons are beeing compared with type Y weapons, when you have type X weapon equiped in Alternate Set.
Nevertheless you can easly switch weapon set, not a big deal but it is kindof annoying. It gets more annoying when you want to compare new underwater weapon on surface. So each time you have to manualy compare the items or you have to manualy drag and drop to switch underwater weapons.
Solution suggestion:
Incorporate a functionality, witch with a press of a button, lets you compare weapons with Alternate weapon set.