clayne: They may be similar in 2D size looking at them from the front, but the F3 occupies a lot more volume. I don't just mean in the sense of how much water it displaces; I mean real-world, how-much-space-does-it-take-in-a-bag-or-a-pocket. I can fit my M3 with a collapsible lens in my front pocket. I couldn't fit an F3 in there even without a lens mounted.