There are debates everywhere about this. The answer has usually been: not necessarily. The sound of a flute is mostly determined by the design and craftsmanship put into it. The headjoint is the biggest factor in terms of sound production. To the player, there may be a distinct difference between metal types, but to the audience, the sound difference is minimal at best. One big debate about plated vs. solid silver is a matter of determining which of the two has a sound closest to the old French flutes (Louis Lot flutes and the like). Some argue silver because they were all solid silver. Others argue nickel silver with sterling silver plate. Nickel silver is actually a type of bronze that has a high nickel and copper content. The old french flutes (while made of silver) had an extremely high amount of nickel and copper in their metal. (They weren't sterling silver).
There are several videos on YouTube about this. Galway has one, Nina Perlove has one...
You just have to choose for yourself. When I personally was debating between getting a solid silver Miyazawa or a Miyazawa with a plated body, I chose to go with the plated body. I used the same headjoint when trying out each. I liked the response of the plated better, and within my budget, I couldn't justify the expense of the solid silver because I didn't hear a big enough difference in sound. So instead I spent the extra money on upgrades (upgraded riser, extra keys, extended warranty, etc.).
The metal debate is endless. I've tried gold flutes that sounded like silver flutes, and vice versa. I have mixed and matched headjoints and you can bet that a good headjoint makes a difference. Even from one silver flute to another (and gold, and platinum) they all have a different sound. They are all unique. I tried a gold Brannen, and the sound was like chocolate on the ears. I tried a gold Straubinger, and it was like sunshine (radiant, resonant, and brilliant, but not bright and thin).
So my answer: no. The metal material does not necessarily make a difference in the sound. I do however have my doubts from time to time.
Another question is: does the metal make a difference in the WAY they play? (Response, Resistance, etc). I think they do make a difference in the WAY they play. It takes a bit more energy to play gold and platinum than it does silver.