I actually picked up the S2 the day it came out and just happened to receive my Moto 360 2 the same day, so I was really able to play with them side by side.
I really like the S2, but it certainly has some fatal flaws, the most obvious is S-Voice. It's just terrible compared to Google, very limited as to what it can do and very slow even when it can do it. The UI on the S2 is amazing, probably it's best feature in my opinion, very fast and fluid, much more so than the Moto. Also, the S2's screen is awesome, definitely small compared to the Moto, but very nice looking and higher resolution. Side by side it's noticeable, but just wearing the Moto by itself, it looks great.
That being said, I really think the Moto (or Android Wear) is better in a lot of ways that count for me. The notifications are much more simple and obvious, you don't have to go look for them like on the S2. Replying or dismissing is just a swipe or a quick talk, very quick and intuitive. Also, a HUGE plus for the Moto is the Google Now integration. You will get Now notifications on the S2, but nothing more. With the Moto you will get the full benefit of Now and it's really amazing. One other thing that drove me nuts with the S2 was when listening to music on my phone; once you are listening to music and the watch returns to the home screen, you will have to navigate back to the music app to do anything! Every time you want to skip a track, change the volume, or even pause it when somebody walks in, you have to tap the screen, rotate the bezel to find the app, and then do what you wanted. Got old VERY quickly. With the Moto, your music is front and center the whole time your music is playing. You don't even have to do change screen to pause or play, really nice.
Anyway, long story short, returning my S2 tomorrow, and keeping the Moto. Hope that helps!