They're pretty close in meaning. If there is a difference, I'd say "how long have you lived here" suggests "so far" or "up till now", and "how long have you been living here" suggests the action will continue into the future. I think only if the listener were about to move house would the difference be noticeable.

Some people see a difference: 1. How long have you lived here? You might ask this question of someone who is a permanent resident. She or he might answer: I have lived here for 50 years. And I plan to die here. 2. How long have you been living here? You might ask this question of someone who is only there on a temporary basis. For example, you know that someone studying in Los Angeles plans to return to her country after graduating from a local university. So she might answer: I have been living here for six months, and I really enjoy it. But I miss my country and am eager to return as soon as possible.

They mean the same thing.

They mean the same thing.

THank you Brad!! I think this is the best answer! Now I understand much better everything... Muchas gracias!!