@Endymio
This is true for some cases, but the actual usefulness of ever lighter mice is heavily dependent on one’s grip and aiming style. Yes, if you palm grip then the heavier mouse will be fine and in some cases will indeed be less tiring. If you fingertip, well, that 130 grams you will definitely feel. There’s a good reason why fingertip-dedicated mice (even though there aren’t many yet) strive to not only be as small as possible (well, short mainly since the entire back serves no purpose there), but also as light as possible. It’s also the issue of weight distribution and balance. Several mice with identical weight might feel quite different in the hand depending on said balance.
For most people though I would agree that beyond a certain point weight reduction does actually very little in mice. But I personally started my gaming in my childhood with something so tiny that I just got used to fingertip and normal-sized mice are not comfortable. This, to be precise:
Yes, Potter branding and all. Not obvious here, but that thing was TINY.