HBS3 backup speed QTS vs QuTS Hero

Hi, I’m in the process of testing NAS to NAS backups using HBS3 Hybrid Backup and Sync with two QNAP TS-464U-RP. Backups are made using RTRR Server and both NASs are connected together with a direct ethernet cable.
The main unit has the QTS firmware and contains a windows backup folder with a size of 42GB. The second unit was tested first with QTS. A pool was created, followed by a volume and a backup folder. Backup time was 47 minutes.

QuTS Hero was then installed on the second unit following a factory reset, a pool was created with a shared folder. Backup time was 3:17 minutes. Nothing changed aside from the Firmware. All firmware was up to date and the file was the same. The result were repeated several times. What explains such a large difference in time? Would it be possible to improve performance using QTS?

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