What is the difference between STD-601 434 MHz and 400 MHz version?

The STD-601 434 MHz operates on the 434 MHz band only and holds CE and EN 300 220 certification. The STD-601 400 MHz can operate on the 429, 434, 447 and 458 MHz bands for wider frequency operation. However it is not pre-certified for operation on any of these bands.

There are various differences in the settings also. See product page for details.