The Redbreast is really quite nice. I've had the Jamesons 12 but not the Bushmills. The Redbreast reminds me of a combo of Old Pulteney for brine, some Talisker for spice, and Balvenie doublewood for the sherry notes. It is superior to the Jamesons no doubt. I don't have them side-by-side so this is from memory. I last had the Jamesons about 3 weeks ago. All in all terrific whisky!
Are you comparing Redbreast 12 to regular Jameson? If so, you really should try Jameson 12, as it is a much fairer comparison. I still think Redbreast wins for balance, though. Jameson 12 is almost completely overtaken by the sherried wood, whereas Redbreast leaves room for lovely malt flavour.