Pebble, has longest battery life (about a week of use) and black and white screen visible on bright sun light. It has the lowest price ($150 at Best Buy). Those two features, especially Eink screen,  are very important and critical for acceptable of the product. Right now only with Eink screen smartwatches can gt more then a week of battery life.  Shortcomings: device in bulky and not very reliable.  Supports both Android and iPhone