The FitBit Flex and Jawbone UP are two of the best-selling fitness trackers on the mark" />
The FitBit Flex and Jawbone UP are two of the best-selling fitness trackers on the mark"/>
The FitBit Flex and Jawbone UP are two of the best-selling fitness trackers on the market, edging out even the legacy electronic names like Sony and Samsung. But in a head-to-head competition, which one emerges victorious?
