After doing a side-by-side comparison of both Synapse packs (19 & 25) I noticed something that prompted me to write this post and make a suggestion.
As you will see in the picture below, the Synapse 19 bottom pocket zipper is located precisely where it looks like it leaves the same room both at the bottom and top of the zipper. In other words, it looks pretty symmetrical.
However, the Synapse 25 has the zipper way too high, leaving a huge space between the bottom of the pack and where the zipper is located. In other words, to me at least, does not look very symmetrical.
I would recommend placing the zipper lower, without affecting the overall size of the bottom pocket. It would just have more "upward" space than it does now, but IMHO will make it look "prettier". Just saying!