It's almost certainly none of those exactly. There's many many ways for a bottled spirit to taste different even if it came from the same distillery. Four Rose

It's almost certainly none of those exactly. There's many many ways for a bottled spirit to taste different even if it came from the same distillery. Four Roses uses two different mash bills (i.e. proportion of grains) and five types of yeast to create ten different new make spirits, which they combine in different proportions for each of their products. Bulleit is probably a distinct combination. It may also be aged in a different warehouse or a different part of the same warehouse (which can have a surprisingly large effect). It may be aged in casks with more or less char than the casks used for the Four Roses products. It may be bottled at a different age. The blender also gets to taste all the mature casks and pick and choose which ones get combined to make the final product, and can create a different flavor profile just with that choice. So rest assured, it's not just a "re-brand", even if it came from the same stills.