They're both highly effective mobility aids.

You'll only be able to get a guide dog if your vision is impaired to the point that you won't try to make navigation decisions. For example, if you could go left or right to avoid an obstacle, you need to let the dog make the decision. Because you have enough vision to travel without a cane, you might not be eligible for a guide dog, but you would need to be formally assessed by a guide dog school.

You'll need good cane travel skills before you can get a guide dog, anyway, so that's the first place you should start. Also, 20/200 vision may not qualify you to get a dog.

My left eye is a prosthetic. I have 20/200 vision in my right and a very narrow visual field due to retina damage in that eye and I feel like a dog is more than I need. My cane works fine for everything I need to do. Breeding, raising, and training guide dogs is expensive and time consuming. Some people wait a long time to get their dogs. Personally, I'd rather the dog go to someone who needs it more than I do.

Guide dogs sound great, because dogs are awesome! But in reality, a guide dog is more than a pet and it comes with a lot more needs, expenses, and responsibilities than your average dog.

They're great for people who need them and have the right mindset, but getting one isn't for everybody and isn't a decision to be made lightly.

howCaseySeesIt on youtube has albinism and talked a lot about her white cane she definitely helped me to make the choice!

Essentially, a cane hits the obstacle while a dog goes around it. I have some usable vision but, so long as you trust the dog and let it make decisions, you should be eligible for a guide dog.

I believe guide dog schools start training people at 16, and even then they try to be careful with teenagers as its a lot of responsibility.