I tested 10vs10 squad battles of dwarfs with identical equipment apart from the hammers (silver vs. steel). The different materials performed pretty much the same when taking unarmoured dwarfs, but when the squads were entirely equipped with metal armour, silver would win with huge margins, never less than 7 survivors, usually all ten (while the the opposing squad was completely wiped every time).
I only ran a few tests like this, but it really seems that higher density helps a lot in getting an effective hit through metal armour. To really do the protective work, the armour must cover all body parts
You can check now the equipment in the screenshot I uploaded in the testing post.
I started the testing with teams of 15 gold war hammers vs 15 platinum war hammers (which didn't help much):
1 round: 4 platinum survivors (2 unconscious)
2 round: 5 platinum survivors (3 unconscious)
3 round: 9 gold survivors (didnt check uncounscious from now on)
4 round: 13 gold survivors
5 round: 9 platinum survivors
6 round: 6 gold survivors
7 round: 9 platinum survivors
8 round: 7 gold survivors
9 round: 7 gold survivors
10 round: 7 platinum survivors
11 round: 7 gold survivors
12 round: 8 gold survivors
Squad battles don't really show results well.
I agree. If one of the squads gets the first two kills then it has a great advantage over the other, and also half of the winning team might be inconscious or severely wounded, you get martial trances, etc.