Well, it's better for me. It has longer run times. I think for the medium mode of 20 lumens, was it?, they give 8-10hrs. On the other hand, the i3s starts on medium, while the i3 starts on low if you prefer this. I THINK.
I've really forgotten, I was in a cycle of buying new ones, then selling them or giving them away to friends and eventually I was left without a single one and haven't had one for a couple of years. I hven't had one since I got into 1xAAA clickies, but the i3s was my fave one back then. The i3s one is also a bit shorter and looks more.. stylish as its edges are smoother by design unlike the "curder" i3 vision. The clip of the i3s is reversible and when you remove it, just pull it, there aren't ugly screw holes left like with the i3 one.
And yes, the newest one, the i3 E has just one single mode.