I'm 15 and have been playing the marimba for roughly one year and percussion for two years. For the past two or so weeks I've learned this Musser Etude (Opus 6, No. 9, in B Major), and I am stuck at what grip to use. The chords are easier to play with Burton (the way I play Burton grip is similar to what W. Moersch describes), but with Burton grip, the small intervals are hard and uncomftorable to reach. I'm currently playing on an older Musser Rosewood 4 Octave (unfortunately I cannot find a serial number on it, and I'm renting it from my teacher so I do not really know the history), and using Encore 32AYR's, which sound very nice on it.

Thank you for your time.

For the most part, you should have a grip that you are comfortable to play most pieces with, so its not neccessarily having to use one grip for a specific piece. I say that at this point, learn the major ones and see which one you like and stick with it. So try Burton, Traditional, and Stevens, and see which one feels the best for you. Good luck!
~Behzad