Hi Scott!
I was riding through Cambodia with an american girl with a pair of XM-40. They seemed to be well put together but was a bit like american cars, lots of features but when you lift the hood you find mostly stoneage tecnology;). They are quite roomy. She brought all her mesuremade suites and skirts(!) she had made in Hoi An, Vietnam, and was to overloaded on the back to enjoy her ride on the bad roads between Sian Rep and Knom Pen. Never go fully loaded on the rear, but put the heavier and smaller items in the frontbag.
I think the compressionstraps are great and I would like to have some on my Ortlieb. Half full the Back/front Rollers have a large front area and are therefor not to aerodynamic. The XM-40 did however seem to have an even larger area when fylly loaded. They also sit very high witch made the bike top heavy.
All those features also means added weight and, in my view, higher risk of something going wrong. There must also be a reason why Arkel offer both rain cover AND drybags as extras. Non of this is needed if use Ortlieb or Vaude waterproof bags.
I must ad have have had some problems with making my Ortlieb Front/Back Rollers Plus with QL-2 atachment hooks yo stay on when I ride on very bad surface so I would recomend the cheeper QL-1. But the top of the line Vaude , with that extra bungee and without the side pockets that seem to brake, have recived very good reviews from well known and independent explorers.