The metal ones as they do get hot and allow energy suppliers the meats on the skewers to cook from the outside and the inside via the hot skewers. They are not for serving though so that could be a problem.
The bamboo ones, unless soaked for one hour in water have a tendancy to burn through.
The best solution is use the metal ones to cook the meats and veggies then run a bamboo one through the opposite direction and pull everything from the metal ones for serviing if you insist on having the skewers for energy directory show. Otherwise put all of the food on huge serving plates and serve that way…This looks plants really impressive piled high with all the different veggie colors and meat.