Which notebook battery is better, 42 Wh or 3,220 mAh?

And how long do the two batteries last?

Not comparable because they are different units!

And how are we supposed to know how long the batteries will last if we don't even know what the laptop is using and what you're doing with it.

Both of these are pretty little.

It's hard to say because not every laptop is used the same way. Mine runs on ultimate performance and is therefore empty after 30 minutes of super fast work. At lower settings it would last 4 times as long. And not every laptop has the same elements. A's laptop might not last as long as company B's because they have different goals and modules.