The cleaner the power the better the sound, hence start with a separate spur and cleaning up your fusebox.There are passive conditioners from Akiko, Acoustic Revive and Furutech which achieve great results without the side effects of active conditioners and transformers. And by the bye…Small power supplies in a high efficiency system have a much easier job than giant torroidals driving transistor amps (EFI et al). In other words: horses for courses rather than simply asking what’s better…
And for the adventuresome among you: try power modulation à la Add Powr or Nordost as well as grounding devices as further useful ways of improving power.
Power conditioners come into their own where there are major voltage variations on the grid, in most other instances they tend to be overkill.