I wanted the smallest possible bag that could still fit my essential gear. I couldn't decide between the 3L and the 6L, so I got both and gave them a test run. Both are amazing bags but one definitely worked out better for me.

Peak Design Everyday Sling V2 3L - https://amzn.to/2Se5p8K
Peak Design Everyday Sling V2 6L - https://amzn.to/3eQorf7