Once the number is recorded elsewhere, what would be the advantages and disadvantages of removing the serial number sticker from the outside of a gun safe?

Tracking it when it gets stolen

Good point.

Seems it might be best to etch the s/n on the back since a sticker can be easily removed.

Check if the serial number is stamped on the safe, interior door or jam.

It only appears on a small sticker on the right side of the safe.

I've registered it with the manufacturer (Cannon) for perhaps a second time. Bought it back in 2015 and can't remember if I ever registered it.

I think the upsides would be able to track it if it's stolen or to do warranty stuff if needed. I don't really see a down side to leaving it on there, doubt a burglar is going to break in to get the serial number and then try to do anything with it.