Hi there and welcome,
Can you be more specific, which Sense the ESP32s3 Sense or the Xiao nRF52840 Sense ?
Both are awesome so you can’t go wrong. If I were starting at the battery which imo makes a lot of sense no pun intended 
Check out the battery life calc. [
Battery Life Calculator
](Battery Life Calculator | DigiKey Electronics)
18350 3.7V-4.2V 1200mAh High Performance Rechargeable Li-ion Lithium Battery
for example 1200 mah at ESP32s3 Lite sleep most of the time 2ma. power use gives you approx ballpark of 25 days cut that in half for head room is what I would do.
shooting from the hip.
HTH
GL
PJSpecifications
| Processor | ESP32-S3R8 Xtensa LX7 dual-core, 32-bit processor 240 MHz |
|---|---|
| Low Power Consumption Model | Light-sleep: ~ 2mA Deep Sleep: ~ 14 μA |
| WiFi Enabled Power Consumption | ~ 100 mA |
| BLE Enabled Power Consumption | ~ 85 mA |
| Working Temperature | -40°C ~ 65°C |