The FAQ lists XEP-0246+TLS as the preferred way to do e2e encryption (hopefully with RFC5081). That XEP, however, is deferred and not recommended for implementation. XEP-0027, however, is historical and already supported by many clients (Psi, Gajim, etc). Implementation of XEP-0246, therefore, is implementing something few (if any) others do, and which likely no one ever will (since deferred XEPs are usually replaced by something else later, and not "reactivated"), whereas implementing XEP-0027 would give telepathy-gabble users in-protocol end-to-end OpenPGP strong encryption that is immediately compatible with existing clients and practices.
The FAQ lists XEP-0246+TLS as the preferred way to do e2e encryption (hopefully with RFC5081). That XEP, however, is deferred and not recommended for implementation. XEP-0027, however, is historical and already supported by many clients (Psi, Gajim, etc). Implementation of XEP-0246, therefore, is implementing something few (if any) others do, and which likely no one ever will (since deferred XEPs are usually replaced by something else later, and not "reactivated"), whereas implementing XEP-0027 would give telepathy-gabble users in-protocol end-to-end OpenPGP strong encryption that is immediately compatible with existing clients and practices.