I have the Flipside 300 and the Streetwalker Pro HD, and while I like both of these, I'm in need of something in between them in side. I've been trying to shoehorn stuff into the Flipside 300 when the Streetwalker Pro HD is overkill, and I've been looking at the Flipside 400 and regular Streetwalker Pro. Anyone ever done a side-by-side of these two backpacks? It *looks* like either would fit the bill for me, based on pictures I've seen of gear inside. Pros and cons of each? Thanks.