Can't comment at all about the Gobi....but I do have caribou cases on the bike. They are fairly heavy by themselves, say 7kg each, and once loaded I would certainly want that added rigidity of the cross bar.
As for loading.....they are sort of a pain and I have found myself wanting some nice top loading aluminum cases from time to time. Though, once you know how to load and unload it isn't that big of a deal. You also have the option of loading them while on the ground, which effectively makes them top loading. I found this to be a bigger pain that it is worth. I just got used to loading them on the bike.
Overall they are great panniers. Very heavy duty, put with lots of abuse without showing it all that much. I wouldn't hesistate to recommend them.....but there is that pesky side loading thing.
"We cant solve our problems with the same thinking that created them"...Einstein