[JThiessen]

If you intend to bend or weld it, 7075 will not work, it is too "brittle" for bending, and does not reset into a stable material after welding.
For machining, 6061 is a bit nicer for the machinst, but 7075 works fine as well. Generally speaking, for our applications in RC, a plate of 6061 will be just as good as a plate of 7075 - unless you just happen to choose a thickness that is right on the edge strength wise. If you are tapping holes, then you will start to see a greater difference over time. When you get into designed NC machined parts, then you will also start to see a difference in material properties popping up. So in a nut shell, don't sweat it.