I don't see my answer up there. You need a third choice: Put down new brown!
How anyone likes that crappy McDonalds mulch is beyond me.... It's just tacky, plain and simple. Throw in some plywood sillouhettes (sp?), some gazing globes, and a plastic pre-formed fountain, and you've got a good 'ole landscape thar Earl!
But seriously, just put it over the old.