It really depends on you. Synology is more plug and play solution which is easy to configure with the most basic applications.
If you want to save some money or get better hardware than used in Synology for the same prize than DIY NAS should be your choice. It will take some time to configure it, however, it is more customizable with a better hardware.
It depends on your use case, if the idea is simply to get the shared storage, the windows option should work there.
I would avoid Storage Spaces since it is too unreliable, especially the parity option. As alternative to it you might use stablebit drivepool with snapraid or collect the drives into software raid inside of linux vm. Shouldn’t be an issue with Starwinds cvm https://www.starwindsoftware.com/blog/file-share-with-starwind-vsan