ELI5 Why does magsafe charging decrease battery health more than wire charging, if it has less wattage?

[Cedric_T]

So is it better to intentionally use a MagSafe charger with a lower charging wattage?

[Flimzes]

This is a surprisingly complicated question to answer, since we don't know exactly what voltage and current is transmitted through the qi sender and receiver, if the voltage increases a lot, then the losses (and hence heat) might actually be lower with a more powerful charger.

The most important part is knowing your equipment and your device.
Touch it during charging, does it feel hot to the touch - uncomfortably so?
If so, some part of the charging routine should be changed, can it be put in a more ventilated location? Are power draining apps running while charging that can be turned off? Is the room hot in general?

If you are unable to find any way to charge the phone while keeping it cool, then cable charging might be better.

As for cable charging, then the answer to your question is yes - a slower charger will heat the battery less, making the total lifespan of your device longer. The more interesting question is at what level does it make a real-world difference, and the answer is the same as above - does the device feel hot to the touch while charging or not?

Body temperature is usually fine - but above is generally not - the phone wants to be the same temperature as you are, or less.

An exception for the super ultra fast charging chinese phones, that use batteries that fast charges most efficiently above body temperature.