E3D High Precision Heater difference
E3D themselves specify this on the product page:

Our high precision heater cartridges feature a rounder cartridge with more consistent diameter and surface quality, ensuring greater surface area contact with the heater block for more reliable heat transfer. With the quick change principle in mind, the high precision heater cartridge uses a Molex Microfit 3.0 connector enabling quick HotEnd changes.

E3D also provide a datasheet on the precision heater cartridge which can be compared to that of the regular heater cartridges.
From an electrical perspective, the are identical. They will put out the exact same amount of heat. The main difference is in the dimensional specifications, which for the precision cartridge is guaranteed to be a diameter of 6.0 mm +/- 0.2 mm and a length of 20.0 mm +/- 0.5 mm, while for the regular cartridge no tolerances are specified though they have the same nominal dimensions.
Apart from this, as we can discern from the product description, the precision cartridge comes with a connector to enable swapping and a better surface finish.