I do not own either Hario, but I believe you will find that the main difference is the hand grip, whether the bigger jar will be easier to hold (or not) when grinding hard beans.
I also think the burrs are the same, but there must be some mechanical difference in how the burrs are mounted as at one point Orphan Espresso sold a lower bearing mod kit (and I believe there is also a similar DYI idea posted somewhere) to better stabilize the burr gap when grinding for French Press. So if you drank FP that model may have a bigger appeal, otherwise the small model has advantage easy storage in a drawer and portability.
I also think the burrs are the same, but there must be some mechanical difference in how the burrs are mounted as at one point Orphan Espresso sold a lower bearing mod kit (and I believe there is also a similar DYI idea posted somewhere) to better stabilize the burr gap when grinding for French Press. So if you drank FP that model may have a bigger appeal, otherwise the small model has advantage easy storage in a drawer and portability.