When comparing Sensoria Fitness Socks vs Fitbit Flex 2, the Slant community recommends Fitbit Flex 2 for most people. In the question“What are the best fitness trackers that pair with iPhones?” Fitbit Flex 2 is ranked 4th while Sensoria Fitness Socks is ranked 10th. The most important reason people chose Fitbit Flex 2 is:
The fitness tracker is completely waterproof and keeps track of your laps, pace, and total duration of your swim.
Specs
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Pros
Pro Provides feedback on running technique through voice messages
Sensoria fitness tracker gathers information on how a runner puts pressure on their foot and analyzes it in real-time. If the sock notices something that could potentially cause injuries, it warns the runner with a voice message and suggests a way to improve his technique.
Pro Motivational audio cues
A virtual coach can be set up to congratulate when personal records get beaten, cheer when doing well, and warn when not doing as well as hoped. The frequency of audio cues can be adjusted.
Pro Allows adjusting settings to preferred running style
There are multiple valid ways of running. To accommodate runners of different styles, Sensoria fitness tracker allows setting up desired landing positions and cadence as well as turn on a metronome to help out with execution.

Pro Easy access to data
Sensoria provides companion apps for iOS, Android and Windows phones, as well as a web dashboard.

Pro Socks can be washed
Though the fitness tracker is not fully waterproof, the pressure sensitive electronic textile used in the socks can safely be washed and machine dried.
Pro Great option for swimmers
The fitness tracker is completely waterproof and keeps track of your laps, pace, and total duration of your swim.
Pro Sleek design fits a variety of occasions
The Flex 2 is a thin band all the way around that has a modern and sleek design. Since it isn't super sporty in appearance, you can confidently wear it for a lot of different occasions without it looking out of place.
Pro The app and web platform do an excellent job of keeping you motivated
The Fitbit app lets you set goals and milestones which reward you with badges and trophies when reached.
You can also challenge friends and family, competing against them for top spot on the leader board.
Pro Replaceable wristband with lots of options available
The fitness tracker itself is a separate part from the wristband that can be taken out and put in a different band. Therefore, not only are there 10 wristband colors to choose from on the official store, a different color of band can be worn every day with the same tracker. There are even custom bands available from third-party vendors.
Cons

Con Unreliable altimeter
The socks sometimes have trouble detecting changes in elevation.

Con Only one sock is active at a time
The socks feed data to a single anklet, and information for both feet can't be gathered at the same time yet. This functionality is planned.

Con Doesn't catch some bad running techniques
Currently the fitness tracker covers a relatively small subset of bad running techniques. It's possible to be in a situation where the technique is bad and the device is not aware of it.
Con Very few customization options currently available
Some of the fitness tracker's customization options are planned, but not yet available.
Con Underwhelming battery life
The fitness tracker's battery lasts about 3-4 days on average.
Con Can't be paired with external HR monitors
The Fitbit Flex 2 fitness tracker has no built in heart rate monitor and lacks the ability to pair with external HR monitors.
