Should I download update 15.2 on iPad 6?

Each update version contains new features, bug fixes and (very often) important security patches too (see these two articles:--> About iPadOS 14 Updates - Apple Support and About iPadOS 15 Updates - Apple Support) .

It is ALWAYS recommended to update your device to the latest operating system version.

And, since your iPad supports iPadOS 15, I suggest that you keep it updated.

Regards

Giulio

I believe you refer to iPadOS 15.0.2.

This release includes essential patches for a critical security vulnerability that is understood to have been actively exploited. Installation of this and future updates is strongly recommended.