which I guess means you are also required to use Chrome on a tablet or smartphone to do the same thing
No, it's built in to Android.
In regard to the Mac and iPhone link, all the photos I take on my iPhone are synced to my Mac so I have copies on both. The photos are all tagged and stored in the same way on both devices. I can send texts from the Mac and make/receive phone calls. The iPhone syncs perfectly with my iTunes music library and again means I have local copies of all my music on all devices.
Yeah, I get all that on Android (well, maybe not tagged photos, I'm not sure, I don't need to tag photo's with Google Photos. Type in 'white dress' and any photo with a white dress in is there, which I would suggest is better). Technically I can call from my PC using Hangouts, I've done it to Canada, the quality was amazing. I'm not sure if UK to UK are free though, or maybe a penny a minute. I can do this with the phone off too.
The Apple Watch screen lights up as soon as you lift your wrist so the screen not being on all the time isn’t really an issue (and if the raise to wake doesn’t work on you want to know the time without raising your arm, you can double tap the watch face).
It's this I want to avoid tbh. Obviously it is seen as a little rude to be checking your watch, so I like to try and be as subtle about it as possible. I can see the recording of runs as a plus, for those that run. Music can be played from Android phones too. I would like the occasional heart rate readings through the day. Directions from Google maps also on Android although no taps when you need to turn, which I can see is a nice plus.
I can imagine, if you lock your PC the unlock when watch nearby being a nice addition too.
All in all I honestly don't think the whole eco system argument is that big a thing. I think Google does it just as well, but they don't limit what devices you include, like Apple do, so for me it possible has the edge.
Again, I'm not trying to start the Google vs Apple or Android vs iOS argument, I honestly was just interested in why it's touted so highly.