> imho the qubes approach is more viable and exposes far less attack surface.
I don't know what you base that opinion on since it's not an easy comparison to reason about. One metric you could use would be actual vulnerabilities. In the last year there have been several hypervisor escape vulnerabilites that compromised Qubes OS VM isolation completely, most (all?) of which have been present in Xen for the entire lifetime of the Qubes project.
By contrast during the same period only one Linux kernel vulnerability (DirtyCow) affected Subgraph sandboxed applications, and it would only have been exploitable using techniques which have not been disclosed in any public exploit so far.
I don't know what you base that opinion on since it's not an easy comparison to reason about. One metric you could use would be actual vulnerabilities. In the last year there have been several hypervisor escape vulnerabilites that compromised Qubes OS VM isolation completely, most (all?) of which have been present in Xen for the entire lifetime of the Qubes project.
By contrast during the same period only one Linux kernel vulnerability (DirtyCow) affected Subgraph sandboxed applications, and it would only have been exploitable using techniques which have not been disclosed in any public exploit so far.