I travel frequently to China for business and would like to buy unlocked iPhones to use in USA, China and Korea. Does anyone have recommendations as far as all the different GSM, CDMA etc go? according to the iPhone product page, there are A1589, 1593, 1586, 1524 models on sale from China and 1549, 1522, 1524 and 1586 models on sale from USA apple website. It seems that models 1586 and 1524 on sale from US would be useful for China, as they feature FDD-LTE and TD-LTE which I think are the China-compatible LTE technologies... but I'm not exactly sure because I've never carried LTE phones across the border. Any advices?