Can't compare them to the Ortleib, but I have used them for the past year all-seasons:

• The rain covers work well, and I've never had anything get wet inside.
• They're pretty rain resistant without the covers, and I haven't gottent anything wet in winter or light rain without the covers.
• They're pretty durable, as I lay them on the pavement every morning, and they haven't worn significantly.
• The mounting brackets work really well on my Delta Mega rack with no rattling, but are a bad fit on my other rack, where the side has an extra hoop that is layered on top of the main strut.
• Best fit is with a rack of any diameter where all side tubes are welded on the same plane, not over/under.
• One of the pair has organizer pockets and key clip that I actually use often.
• The compression straps are very useful for compressing light loads and reducing bulk.
• They're small enough to use on a front rack if you want.

I'm happy with them.