I have an Arkel large handlebar bag. Better mounting system than the Ortleib or Jandd in my opinion. Mine is older and isn't fully waterproof, but I haven't had any issues with the inside getting wet or damp the few times I got caught in the rain. I believe the current version is fully waterproof, as is the Ortleib. The Arkel has a large main compartment, an inside compartment in the top of the bag, two front pockets (one zippered at the front with an open sleeve behind it, and a mesh pocket on each side. It also has the customary plastic map case that attaches to the top and a shoulder strap. You can also get extra mounting brackets to use the bag on multiple bikes (I assume the other brands do as well). I probably could have gotten away with the smaller bag, without affecting the way I use it.

I don't use a rear trunk when touring, but have a cheapo, no-name, shoe-box shaped, soft cooler type that I sometimes use for day trips when I want to have the ability to keep something to eat cool. Arkel has a nice looking rear trunk that matches their bags.