Making money enchanting means standing around in a city offering enchants, or heavily playing the AH (buy things based on what they DE to, DE, sell mats for more). It also requires buying recipes or grinding recipes in the world, in addition to the basic training costs per level.
Making money with herbalism means getting out into the world farming. There’s no real upfront cost (only the training cost for each level).
So, really, do you want to spend time farming or standing in a city? 