KVM Virtual Machines cannot be downgraded 

They can only be upgraded as the disk drive space allocation cannot be shrunk. It is simply impossible to shrink a block device once it has been expanded to a certain size. If you want to downgrade a KVM server in the future, you will need to create a new server and manually transfer your data.

Live Statistics / Usage will not be visible in the Webdock Dashboard for KVM instances

As KVM instances are much more isolated (i.e. fully virtualized) we cannot read live usage statistics such as current CPU and bandwidth use as we can with our Webdock legacy LXD VPS instances. If you want to monitor usage live, you can SSH in to your KVM and install/run "htop" or install something like Netdata on your VPS.

LXD-Agent is Required to run in your KVM VPS

Once you spin up a KVM VPS server with us, you may notice a small daemon running in the background called "lxd-agent". This is a piece of software which enables us to do all the cool things we can do in Webdock - such as install software, run commands in your server to add shell users, pull utilization metrics from your VPS for our statistics and much more. LXD-Agent is so important to the well-being and operation of your VPS in fact, that we have decided to add this as a strict requirement to our Terms and Conditions.

You cannot mix and match LXD and KVM instances

It is unfortunately not possible to spin up a KVM instance from an existing Webdock LXD VPS snapshot image, or vice-versa, as the two modes of virtualization are mutually incompatible.