The whonix setup has tor and your browser on different VMs, whereas tails relies on linux' firewall to funnel traffic through tor. Tails is "just" one kernel exploit away from deanonymization.

More importantly, qubes is far superior to anything else for day to day security. You can do your banking in one isolated domain, your "let's download a thousand unverified dependencies from strangers" development on another, your internet browsing in a third, you can create domains with no internet connectivity to store your private files, and it's a lot easier than trying to juggle VMs yourself. A side benefit for the people who never close tabs is that qubes never becomes unresponsive due to running low on memory.