SOBRs have some limitations:
https://helpcenter.veeam.com/docs/backu ... ml?ver=120. Generally there are ways around most of the limitations, so it's not a show-stopper. However, you must have appropriate licensing to use it.
You do gain the benefit of having a separate array to store your backups. If you lose the wrong disks in your 60 TB volume, you lose everything. With two 30 TB volumes you only lose what's on the one volume (unless of course you lost enough disks on both volumes, but that's less likely).
There is also balancing data across both SOBR extents. Veeam will balance that to a degree, but you may be looking at running a few active full backups to ensure Veeam balances the VMs across extents. Also, make sure you're on v12 (preferably 12.1) to ensure your backup chains are in per-vm backup mode (if you don't have it set that way already).
Once you have a SOBR up, it can make migrating backups out of the old volumes easier in the future when you want to replace the repositories themselves.
I would encourage you to use ReFS at least, or XFS on a hardened Linux repository to get the most bang for your buck with your repo (block cloning and immutability if you use a HLR).