Ultimately it’s a matter of personal choice and risk tolerance.
The Z1 will be simpler and have larger capacity, but if you have a drive fail you’ll need to quickly get it replaced or risk having to rebuild/restore if the mirror drive follows the first one to the grave.
Your Z2 setup right now can have two drives fail and still be online, and having a wider spread of power-on hours is usually a good thing in terms of failure probability.
I manage a large (14,000±) number of on-site RAID1 arrays in various environments and there is definitely a trend for drives shipped at the same time to fail at roughly the same time. It’s common enough that we often intentionally swap drives out before shipping a new unit to the customer site.
On my homelab, I’m much more tolerant of risk since I have trust in my 3-2-1 backup solution and if my NAS goes down it’s not going to substantially affect anything while I wait for a drive replacement.
nah it’s just a three-dude-wide strip between the bus stop and the bedroom