I was looking closely at the sale Sun Mountain 3.5 as well. The Ogio Vaporlite was 100 so not any cheaper plus it's an older bag. Reviews on Ogio quality are mixed.
I love the Woode divider concept but it seems the consensus is the Sun Mountain bags are better built and lighter weight. I only walk FWIW.
Sun mountain h2no 3.5 lb back is gorgeous