TL;DR
- The European Council has ended its adoption procedure for rules related to phones with replaceable batteries.
- By 2027, all phones released in the EU must have a battery the user can easily replace with no tools or expertise.
- The regulation intends to introduce a circular economy for batteries.
It depends on the layout of the phone though. Size of camera module, placement of fingerprint sensors, other sensors/modules, heat sinks. You name it, really.
As such the batteries tend to be oddly shaped, and even spread out in different places to get as much battery in as possible.
The “best one” differs from phone to phone.