Comparing

When writing a literacy narrative essay  most of the time the audience is a professor, or someone who will evaluate your paper as a grade. In an Ad analysis it's usually the same audience but they are looking for something completely different when it comes to writing. When writing an Ad analysis paper your audience is looking for a lot of detail, adding your own interpretation and being able to persuade the reader to have the same point of view as you do. This is why it's important to have a lot of good reasons to back up your argument.
In a Literacy Narrative essay you are telling a story which has to do with something personal that you have been through and an Ad analysis is just analyzing an Ad and thinking about who its targeting, what's the purpose of the ad, and many other details that might stand out to you.
Stance- Both papers will most likely be written in paragraph form and will not be much different. You might want to add a picture of your Ad, but if you have a good detailed paper it should not be necessary.