What is the benefit, if any, of opting out of the centralized partnership audit regime?

There may be several reasons to opt out of a Centralized partner Audit Regime. here are a few to consider.

1. If any audit finding is taxed is found, it is  taxed at the partnership level at the max individual tax rate.
2. It allows  each partner the freedom to decide how they wish to handle the IRS.
3. It makes a partner at the time under audit be on the hook for any assessment as opposed to whoever is a partner when the audit actually happens. If a brand new partner comes on board, they are liable for any assessment made even though they may have not been a partner at the time of transgression of the issue being audited.

These are a few things to consider on whether or not to opt out.  Here is an IRS source that is really handy that explains eligible partnerships that can opt out as well ineligible partnerships. This has a lot of useful information that may prove beneficial.