Macro lenses usually have high quality, so the Tamron lens should be okay. However I chose Canon because it has image stabilization. My Canon 100mm f/2.8L IS has excellent quality and allows me to take handheld macro shots without tripod when I travel or hike. Of course macro shots often need a good stable tripod and a ring lite (or macro flashes) to get the best and sharpest results. This is because you often need to use a small aperture to keep your tiny subject in focus. However, I really don't like traveling with my heavy tripod. Besides the little creature often has escaped before you finish setting up the tripod. So I do like Canon's image stabilization feature very much.
As for focal length, longer focal length will give you some safer distance to work. Some tiny creatures are poisonous. Good luck!