Well, I can tell you that Stevia is not man-made; it's a plant extract that's really sweet, but also slightly bitter in large quantities.  It's also really expensive, and I've never baked with it so I don't know how much you'd need as a replacement in a recipe.  Agave is a good sweetener but it is still sugar, and you also have to watch your liquid levels in a recipe and doesn't work so well if you want a crisper cookies - it leaves baked goods really moist, which is usually a good thing.  Sucanat is the most whole form of sugar, meaning it's the least processed and retains the most nutrients of the sugars available, but it also leaves things with a darker color and has a slightly molasses flavor, which is nice in the appropriate dishes.  florida crystals is dehydrated cane juice and i think the closest to refined sugar, so in recipes it is probably the easiest to switch out.  hmm that's all i can think of for now, but i can come up with more, I'll let you know!  Oh and brown rice syrup it a great sweetener, really thick and sticky, and the best for your body to process bc it has a low GI number and is a more complex sugar with a mix of sucrose, fructose, and glucose.  i hope that helps a bit!