Guys, this may be one of the most complicated magic systems you've ever seen but trust me. You'll catch onto it pretty quickly. Especially when you get to know the wand and when the wand gets to know you. So here we go.
Each wood has its own perks. This goes the same with the cores. Each combination of wood and core makes different effects. Some woods are especially good with charms or transfiguration while some may be better at offensive spells. However, cores may counter that. Say you have a willow wood wand with a phoenix feather core. Willow wands are excelent for charms and healing while phoenix feathers make a great variety in spells. However, the users of phoenix feather wands may take a little longer to master the spells. See? Willow is great at mastering charms and healing spells quickly while phoenix feather makes spells longer to learn. So how does this work? Well, the wood is dominate in situations like these. You will take a shorter amount of time to master healing and charms versus taking longer. However, with the rest of the spells, it would take longer to master.