Just take a look at VBoxManage --help for a crazy list of settings and features that VBox has accumulated during the past ~10 years.
It even supports ATA TRIM so your fs-driver can discard blocks and keep the VDI-file deflated at all times.
Performance-wise: Compiling stuff within VBox on an i7 quad-core (-j5) is almost as fast as native. X on Linux-VMs feels native too, especially when running in fullscreen.
I was happy with VirtualBox's (on OS X) performance until I bought VMware Fusion. I didn't do any benchmarks so I don't have numbers to back up my claim but it definitely "felt" much faster than VirtualBox.
You may add: excellent documentation and friendly support (board, irc, list).
If I'll ever have to switch, I'd first need feature-parity.
One dirty detail is that the Docker containers need to communicate with the host machine (the dev-Mac). Would this be achievable with the limited bridge that Veertu supports?
Docker for Mac is a Linux VM, in (a fork of) xhyve which sits on top of the OSX hypervisor framework - the same thing backing Veertu.
Curious to the issues you're experiencing and if they disappear if you move to Veertu.
Apparently, this can be worked around using a TAP/TUN device but I haven't tried it yet. Perhaps a similar workaround is feasible on OS X/macOS.
I tried converting a linux vm I frequently use via vagrant just now, and it seems to work well except for network bridging: You can't bridge over wifi. Kindof a deal-breaker.
The relevant page[1] explains it thus: "Due to features of wireless protocol, level 2 bridges don’t work over Wi-Fi, and so you can’t use wireless interface of your Mac to route bridge traffic to external network – only among VMs and host."
[1] https://veertu.com/knowledgebase/vagrant-setup-instructions/