The Visacha certainly seems popular, but it seems to me it has two shortcomings:
1. Must dig deeeeep to get at stuff when the bad is near full,
2. Not waterproof.
The Ortleib seems to sit so high, and the mounting bracket seems to take up valuable handlebar space.
I have three different brands of feed bags but haven't used them on anything longer than 200k. They don't seem to have a high mark for useable volume per surface area, though they are nice ditty bags and fit into tight spots.