Having looked over the photos on the Tom Bihn product pages of the Synapse 19 backpack and the Synapse 25, I feel that there aren't enough side-by-side comparison images of the two Synapses. There should be more. I did not find any comparison images on the Synapse 25 product page, and only one on the Synapse 19 page.
There are a few comparison photos on the Tom Bihn Flickr set for the Synapse 25, but none for the Synapse 19. (There is also a neat comparison photo of the Synapse 25 and the Smart Alec in the Synapse 25 set.)
This got me to thinking: there aren't enough comparison photos between the various Tom Bihn backpacks. Comparison photos can be very helpful in deciding what kind of backpack you want. The Bihn merchandising web-site needs more comparison photos, and more need to be posted to the Flickr account. There also needs to be more angles for comparison photos; not just the front and side.
Here's what I'd like to see for the ultimate comparison photo set: multiple photos from different angles, grouping of Aeronaut, Ego/SuperEgo, Synapse 19 & 25, Smart Alec and Brain Bag.