A recent study has investigated the effectiveness of surgery for the treatment of Achilles tendon tears. This particular study, called a meta-analysis, groups together data from multiple research papers to try to look for trends between multiple different studies.
What the researchers found, is that when the right rehab is performed, there's no significant difference between surgical and non-surgical treatment. If functional rehabilitation is not available, then surgery may help prevent re-tears of the Achilles tendon.
The critical factor identified was the type of rehab when patients had non-surgical treatment. Functional rehab means patients have early motion exercises started. Immobilization leads to a higher chance or re-tears, and therefore, if function rehabilitation is not available, the authors recommend surgery.