We like the JST PH 2.0mm pitch cables because they are cross-compatible with Grove/Gravity. But they're a bit large for smaller breakout boards and wearables. So, for smaller I2C devices, we'll use the JST SH that SparkFun Qwiic uses, so that Qwiic & STEMMA QT sensors are cross-compatible!
STEMMA QT devices keep the level shifting/regulator, so you can use STEMMA QT with Grove/Gravity/STEMMA/Qwiic controllers at any voltage range, safely!
Here's an example of a STEMMA QT sensor board. You can use it with any Qwiic board or device!
You can see how the larger cables are way bigger, and we can't keep the sensor boards nice and 'cutie' without the smaller QT connectors
STEMMA QT ('cutie') 4 Pin JST SH - These are smaller 1.0mm pitch connectors
They are for I2C use when the larger JST PH connectors won't fit on a small sensor board!