That's the cleanest and easiest to do. It's all doable by hand but there's a lot of ZFS datasets (with specific options) that should be created and the installer does it all automagically for you. And it's always nice to start with a fresh new install every once in a while. Definitely create a backup of the old system, you can selectively restore some items from it, like specific configuration files. Files from your home directory perhaps.
