For beginners, there are flutes with a curved head joint, which makes it shorter and easier to reach the keys. Plated flutes are lighter than solid silver, which is the only real difference in metals.
Silver content does not change the tone of the flute. Anyone who tells you differently is trying to sell you something. The real difference between student and professional flutes is the cut of the head joint.
Another thing that does not make a difference in tone is open holes. The only reason these are necessary is when playing modern pieces that call for only partial covering of holes, creating a more airy tone. There are plenty of professional flute makers who produce closed-hole instruments, and plenty of professional players who use them.