yeah, DEFINITELY buy a complete bike. You don't wanna waste your time buying parts, you wanna ride! (I think...). Anyways, all of the bikes you listed will come w/ good parts that will last as long as you want them to. Just pick the one that you are most attracted to and go w/ it. There are some differences in geometry and components, but they are all going to be at least decent. Just get one and ride!