Delete Metadata check on/off?

Hi,
The process of optimize my whole web (http://neurorgs.net) has been completed with the cloud version. It’s works very good. (May be it lacks some statistics to show the overall size reductions…).
I have one question regarding the check in the ewww setting panel: Delete Metadata
1) I’m not sure how this affect to.
In my case, and in the way a use images…I don’t think deleting metadata could be affect to my site…but I suppose this is a no-return operation…so What the trade off is deleting images metadata?
(sorry for my poor image concepts knowledge)
2) How much improvement could be achieved deleting metadata form images ??

Thanks a lot
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https://wordpress.org/plugins/ewww-image-optimizer-cloud/