4 URLs lead to the same page content, are 301 redirects better or setting rel canonical better?

All the following pages have the same exact content:

1. http://www.example.com/seo-url (rel canonical URL)
2. http://www.example.com/ID1234
3. http://www.example.com/content/ID1234
4. http://www.example.com/ID001234

Currently we have set rel canonical to http://www.example.com/seo-url on all the links.

This means that if you open URLs 2-4, they will open with whichever URL you use. While the content is the same the URLs are different.

Is it better to apply 301 redirects to URLs 2-4 so that they all lead to the same location (URL 1) and open the same page content only on URL 1.

I have a feeling that 301s would be beneficial to our rankings.