That rather depends on your definition of "best". If your is "go to all the trouble of repartitioning your hard disk, run through the install process and risk the bootloader no longer giving access to your existing distro" that statement may be true. For most people I would say that booting from a live disc is a far better way of gaining a quick overview of what the distro is like.
If the makers of the various distros actually bothered to document how their boot scripts work and what arguments to pass them, there would be more installable distros on multiboot DVDs, but they don't and sometimes it is just not possible to work out how to do what you want, even if it could be done with a previous release.
Edited to put an "r" in makers towy71
"Insanity: doing the same thing over and over again and expecting different results." (Albert Einstein)