I haven't used the SW3 but I've been using the Moto 360 Sport for the past week and it's mixed bag. HR monitor seems to work reasonably well, and I like the Moto running app and Moto Body. Battery life, which many people complained about, has also been fine for me.
The main problem for me with the Moto Sport is the music cutting out regularly when I run (using Plantronics BackBeat Fit headphones). Lots of other people have had this problem as well. I've tried it on both wrists and that only partially helped. That's one of the killer features of Android Wear for me, otherwise I would just get a Garmin.
So hoping the music will work better for me with the SW3. I have an Xperia Z5 Compact and use the Sony music app so I figure syncing between the SW3 and the Z5 should work well.
My only question on music is since I mostly have FLAC songs on my Z5, and I only want MP3s on the my smartwatch, is there any way to easily transcode the songs as they transfer over from the Z5 to the SW3?
Thanks.