When it comes about Lumberjacking human gets more logs but have a lower chance to get special type of wood. Elfs got higher chance to catch Yew, Ash, Heartwood etc logs. So at the beginning it's good to use human because you need planty wood for training fletcher, carpentry etc you will get wood just faster. After you become GM with carpentry, flecther and lumberjacking its good to change race by quest, because at this point it's better to have higher change of getting special resources than ~2 more logs per chop.