Without ZFS, when a drive starts making mistakes, it starts to corrupt some of your data, so it has to be replaced ASAP.
With ZFS RAIDz1, each transaction is double-checked and errors are corrected, so you don't need to replace any drives until one of your drives is almost completely unusable.
Kitty if you have a GPU and run programs that have a lot of output (build scripts and emerge). It uses the GPU for better performance.