Quarry is a non-trivial user of the Wiki Replica databases and a place where a growing number of users run analytics queries which can consume a large amount of database resources. Now that the new Wiki Replica servers are on-line and ready for full use Quarry's configuration should be changed to use them.
As mentioned in the WMCS blog post, the new servers are lacking some curated data such as the u2041__ores_p database, but this will only impact a small number of users and will eventually be resolved by T173511. Switching Quarry sooner rather than later will benefit Quarry users by giving them access to the larger, faster servers. It will also remove load from the existing servers which could die at any time.