Pro Gives you the chance to fix problems without relying on support
If you mess things up in your Linode instance, for example with the filesystem or boot configuration, Linode allows you to run a recovery ISO so you can try and fix things yourself without relying on Linode's support team.
Pro Allows you to do things that usually can only be done if you have access to the hardware
Linode allows you to create memory partitions and copy or move them around. Furthermore, it even lets you reboot your instance with smaller RAM in order to simulate how your application would act if your Linode instance gets downgraded.