I recommend metal, if you're allowed to wear them. (Some leagues don't allow them for younger kids. It's a safety issue.)
I've always liked Nike or Reebok. Mizunos are on the heavy side. Ringor's are very heavy, too. There's not much cushioning in Puma. Adidas always felt tight.
Nike comes out with new spikes every year, but you can get great deals on last year's stuff at discount baseball sites like FogDog.com. Then, polish them up all black and no one will know the difference
Let us know what you decide.