i’m not sure which birkenstock sandals to get..?

i’m trying to decide between these:
http://www.birkenstockusa.com/products/women/sandals/milano/soft-footbed-cocoa-nubuck/3450
and these:
http://www.birkenstockusa.com/products/women/sandals/arizona/cocoa-nubuck/5132

though i’m wondering if nubuck is the way to go..
what is more comfortable…with or without the back-strap?
and also, what are the advantages of a soft footbed vs. a normal one?

this is my first pair of Birkenstocks so i’m a little lost and i really don’t want to regret what i buy..what do you suggest?

please answer as soon as possible because i really want to use them as much as i can this summer.
thank you!

Tags: Birkenstock, get.., sandals, sure