We recommend you upgrade firmware v1.03 for Xpress.

Neo X-copy algorithm which was used at ND2525 is implemented.
The backup speed increased by 50%.

Two firmware for download.
OTG V1.21 is for original Nexto-OTG while OTG Xpress V1.03 is for new Nexto-OTG Xpress.

The HW difference between these two device is minor. So you can use both firmware at the same HW. But because of minor HW difference, the battery indication might be some different. So use Xpress V1.03 only at OTG Xpress and OTG V1.21 to Nexto-OTG.
The firmware functionality and performance is same for both firmware.

The major update at this version is following

1. Nexto-OTG can Sync between Nexto series.
If you connect Nexto-OTG to another Nexto-OTG/Ultra/CF, then Nexto-OTG sync the back up directory.
The target device should be powered by power adapter.

Thank you for your response. Could you please explain me the difference in detail, if it is not secret?

It is about the battery indication. Users may seldom become aware of it because it is so tiny.