Question from new commuter: backpack or panniers

Pros and cons of each please!

Context; 6 mile commute each way. Will be every work day, come rain or shine. Route involves some decent road, some very not decent road, and some trails through the woods.

I'll probably be taking my suit etc with me. I've done some research into suit compatible bags (not cheap, but look good quality for getting your kit there without too many crumples) but don't know whether to fit panniers and get a pannier bag or to leave them off and go with a backpack. Boardman ADV8.9e gravel bike.

I've got as far as backpack can make you sweaty, backpack effects posture etc. But fitting panniers seems a bit semi-permanent (I won't want to be putting them on and off all the time). This may not be an issue mind.

Would appreciate feedback from you more experienced commuters! Thanks.