Selected answers from the Dumb SEO Questions G+ community.
Benj Arriola: I generally prefer a 301 redirect over a canonical tag.
Now the specific issue with default.aspx, it has to be a conditional redirect where it reads the URL path or the server variable REQUEST_URI and the condition is to check if default.aspx is in the URL or not, if it is, then 301 redirect to the URL without it.
Without the conditions, you end up in an endless redirect loop.
Only if there is some trouble in implementing this, then I will go with the canonical tag.
Bilal Anwar: Use 301 redirect on which page you want to rank and use canonical tag as well to avoid duplication issue in future