I was going to get my wife an Apple Watch for Christmas, but she has muddied the waters recently by telling me she's keen to try a Samsung for her next phone (she currently has an iPhone 6S).

So I'm looking for recommendations for a smart watch that will work reasonably well with both iOS and Android devices. I know there will be compromises when doing this, especially on the iOS side. But I'm looking for the best supported feature set between both platforms. 

From my initial investigations, the two best in this category seem to be the LG Watch Sport, and the Samsung Gear S3. Both obviously have compromises when paired with iOS, but my main concern are their size. They both seem reasonably large and masculine, so I'm hoping there may be wearables with smaller faces that I should be considering too.

I'm interested in reasonably strong fitness tracking support, and would like as many other smart watch type features on top of that as possible. Contactless payment support would also be nice (for BNZ debit cards), but judging on my wife's distinct lack of interest in me whipping out my iPhone for Apple Pay, I'd not put that in the "deal breaker" column.

Are there any other watches or smart wearables I should be considering for this?