Aside from Jose Bethancort - rattan handles were the accepted in the US (in Europe there where always wood handles on xylophone and glock mallets ??) and then the stiff (birch?) handles came in. What are the advantages and drawbacks? Marimba only or also Vibes? Diameter? Length?

the only difference between birch and rattan shafts is the flexibility. Its common for u.s. marimba mallets to be made of birch due to the prevalence of musser/stevens grip in america. The Birch just feels a bit better with stevens imo. The grip is so flexible that you need something stiff to conteract you freedom in your hands. Rattan seems more suited to burton grip due to the less hand motion. And the flexibility lends itself nicely for dampening vibe bars. As for Xylo/Glock mallets, there is a variety of both shafts. Most choose rattan because its more durable than birch and your mallet shaft inst likely to break as easily.

Length and Diameters vary, thats up to personal preference.

I prefer a longer birch shafts with large diameters to get the sound I look for on the marimba. I look for longer, wide rattan shafts for my vibe mallets as well.

if you have any more questions, fee free to email me.