For our two week trip to Europe in the spring, I took a pair of VERY comfy Amalfis "Taher" (in black):
http://shop.nordstrom.com/S/2889258?...=searchresults

as well as a pair of Josef Seibel "Adrianna" sandals:
http://shop.nordstrom.com/S/2861878?...=searchresults

The black Amalfis went with casual to dressy, hot to cold, and the sandals were great but also very comfy when we got to warmer weather in Spain. I think you need to decide on what feels good to you - I had actually bought a more expensive, other brand, but once I put the Amalfis on, I knew they were perfect. The sandals back strap is attached to the sandal with elastic, so no rubbing on the back of your heel. And definitely wear them at home before you go. We traveled pretty light for a 2 wk trip, just a carry on and a medium suitcase. I wore the shoes, & packed the sandals, which took up very little room.