Virtual computers in a virtual world
The method I like the best for evaluating different operating systems, whether they are different Linux distributions, BSD, MacOS or the latest windows offering, is to use virtual machines. This means that with the quality of virtual machine programs available now, these operating systems you are evaluating run at near native speed. In fact you would be hard put to notice the difference with relatively modern hardware.
Even better is that while you are evaluating this new and exiting version of, say, Ubuntu, Mint, Fedora or Arch Linux, your existing operating system is also active and can be used at the same time. Providing you have enough memory and CPU power you can have more than one virtual machine running concurrently. On my pretty standard (sub standard by today's standards) of an AMD 5200+ CPU and 2Gb ram I have had three virtual machines running side by side as well as my, at that time, Debian operating system serving web pages and managing email. With a good virtual machine program, I use virtualBox myself, you are only limited by the amount of hard disk space and ram on your beast box.
Using a virtual machine program you can easily create and delete your virtual machines, making evaluation of different operating systems an easy task.