To a certain degree, it comes down to what you prefer. As already mentioned, ZFS has the additional layer of checksumming everything, therefore being able to detect bit rot. It does need a bit more RAM, depending on what you plan on VMs and how much resources they will need, a bit more RAM might be good.
The one big reason why I personally prefer software RAID is the fact that I can access the RAID from another system that supports it. Should the HW RAID controller fail, you will probably have to get the same model with a similar firmware to get the RAID back working. With Software RAID you could even plug the disks into another system and still get to your data.
If you plan to use ZFS, you might want to replace the RAID controller with a simpler HBA, especially if it is a Gen 8 or older. From what I heard, the newer models have a somewhat okay HBA mode that allows you to boot from it if in HBA mode. Ideally, you still change it for a simpler HBA controller.
Regarding ZFS pool layouts: please have a look at
https://pve.proxmox.com/pve-docs/pve-admin-guide.html#sysadmin_zfs_raid_considerations .
The TL;DR is that any RAIDz layouts will have a usually unexpected space usage overhead for VM disk images due to parity. To avoid that and for better IOPS performance (what is usually needed more for VMs) consider a pool made up of mirror vdevs (RAID 10 like).
