I went with the larger size because of the speaker support. With the latest Android Wear update you can make and receive calls.
The larger one has a speaker, and Google has confirmed it can be used for Bluetooth calls.I'm not 100% sure but I think none of the Zen Watch models have a speaker, so even if the updated Android Wear app supports making calls I don't think the ZWs will be able to do that.
Gerry
You're wrong. The bigger model absolutely has a speaker. It was confirmed by multiple sources a long time ago and Google even mentioned the support in its blog post. Those of us with the bigger model will be able to make calls when we receive the new update which was announced today.I'm not 100% sure but I think none of the Zen Watch models have a speaker, so even if the updated Android Wear app supports making calls I don't think the ZWs will be able to do that.
Gerry