7120 data and physical device migration question. [Factoryreset vs.. Unconfig]..

Hi all;

I would like to data migration method by based system changing.

Current system : (We would like to call it 7120_old)
ZFS7120 has two pools (pool-0 for file system for NAS, pool-1 has LUN for SAN).
7120_old has 1 * J4410 full shelf (total 36 disks included base chassis).

Target system :
Cu buys new 7120. (We would like to call it 7120_new)
They would like to pool-1 (data for SAN) from 7120_old to 7120_new.
We can get the downtime for physical J4410 box removement.

I would like to ask you which method is prefer for data migration.
I had experience for NAS volumes to factoryreset or unconfig pools. At that time, there be no problem to import the pools.