I have both and, if they were both at room temp, I doubt I’d be able to tell the difference. BUT, I’m totally willing to accept that there are those that are far more sensitive to mass than I am.
It’d be interesting to see weight distribution analysis of the two compared. If it ends up being that 10 grams are spread evenly over the entire size of the device, then that would be less likely to be detected than, say, putting two nickels in one spot. For most folks, it’s very likely a non-event. And, seeing how some of those folks go on to put on cases that weigh 80 grams or even more, unfortunately, I’d say that they CAN get heavier. Apple likely sees it as, “If the delta of mass increase is a small percentage of an average case mass, most people won’t notice”.
