Ciaz Vs City; CBU Vs locally assembled, good build quality, fuel efficient engine based on latest K series engines by Suzuki, some safety features not found in City, a comparatively latest vehicle based on latest tech. as compared to City which is 5th generation and at least a decade old model, comparatively good sound proofing, reliability, suspension is also good, etc.
For more details, you can check Suzuki Ciaz owners & fans club page here on this forums.
As far as I can recall, I never heard any Ciaz owner complaining about any issue(s) in their rides, other than resale; which of course has nothing to do with the technicalities & schematics of Ciaz.