I have recently bought NI's Mallet Flux for their cinematic mallet textures, but I was surprised that they have awesome sounding single instruments in there, eg a lovely marimba. Not sounding symphonic, but crystal clear and beautiful!
I've got the Orange tree samples one, but find it doesn't really mix well in my tracks.
From listening to demos, my favourite is the Spitfire one, but I haven't tried it.
At the moment, as it's 50% off and comes with Xylophone, Glockenspiel, Tubular Bells, Glass Marimba, Song Bells, Vibraphone, and Crotales as well for just £80, I think Vital series: mallets from Vir2 is worth considering.
Just checked out Mallet Flux....wow that thing is awesome. It's just increasingly difficult to purchase a full price product now when everything else is on sale.
Yes the Soniccouture Grand Marimba is great. Very full and rich. But the Spitfire Ricotti marimba offers a worthy alternative depending on the type of track I'm using it in. There's a more pointed, percussive sound to it. And the tremolo I find more useful. My recommendation is to get both if you can swing it.