There is that, though I suspect you also mean acts different rather than feels different, as I was talking about function rather than feeling (I already alluded to weapons feeling different). But when I say functionally comparable I'm partly thinking of qualitative aspects such as short-range vs long-range, and precision vs scatter-shot, rather than exact degrees of effectiveness. It certainly wouldn't be surprising for advanced-race weapons to be more effective, type for type. From a gameplay point of view though, the designers might not want things to be too far in favour of the advanced race, or the other weapons might seem unattractive and get underused.

As a side point, where did this 'sandbox' term come from anyway? I've heard it a number of times in connection with gaming and it's always seemed odd to me. I'm guessing it's supposed to mean something like 'collection' or 'array', but I actually just checked Wikipedia and I don't see any relevant definition there.