You guys are starting to convince me not to be such a minimalist
With the 20L bag I'll have room for a nice dry blanket in the bottom, so I think it's gonna be the bigger bag for me.
Plus it works out almost exactly to the value of the gift card, so there's no dicking around with 10 bucks or so left over from buying the smaller bag.
Now I just need to do one more check on Amazon to see if there's anything I want even more