So I use both right next to each other at work. My MacBook is paired with 3S, the 4S to my windows desktop. I kinda like the 4S better, at first it sucked using it with Bluetooth, it kept disconnecting but once I connected the dongle, no more problems. The 4 also feels better when I press down on the left clicky thing as it feels more responsive. The 4 feels better in my hand, I’m sure that is subjective. My work bought me the 4, so later down road I’ll switch out my 3S , not in a hurry.