The Fitbit Sense 2 and the Fitbit Versa 4 offer similar experience but the former offers more features.
The Sense 2 offers ECG readings, skin temperature sensing, and real-time stress tracking and everything else found on the Versa 4.
The Versa 4 is a minimal upgrade over Fitbit's older-gen Versa 3 and has some connectivity and tracking issues.
Case size of Sense 2 is 40.5mm while that of Versa 4 is 40.4mm.
They both have a small side button that can be used with the watch's touchscreen controls.
Neither supports third-party app access, or allows for any music storage or playback via something like Spotify.
The Sense 2 is superior to Versa 4 in health and fitness tracking performance. It is reliable and can connect to GPS signals faster.
The Sense 2 is also a better health tracker with its skin temperature sensor, real-time stress tracking, and ECG app.
Both watches have a battery life of roughly six days depending on usage.
Overall winner: Sense 2. It does not have third-party app support or the ability to store or play music but it has better GPS connectivity, health tracking features, and access to ECG apps and heart rhythm data.