2 is similar to 1 but with minor improvements. The design of 3/3S is going well for me, I'm on year 2 and it's aging pretty nicely for me. Some discolouration in the silicone, but pretty much anything in contact with your (sweaty) palms will degrade or discolour over time. Functionally, the 3S seems to be the best. Takes all the functional improvements of the 3's design (USB-C, better ergonomics, buttons, magnetic scroll wheel) and then makes all the switches silent and extremely long life.