Tough call, but to my ears I'm going to have to say the Smoothie is little fatter and warmer. But I am a total fan boy for this compressor so take that for what its worth.
Comparing the Diamond and the Smoothie, I find the Diamond to compress/limit a little more but part of that is a mix a fair amount of dry signal in with the Smoothie. If I want fat tone I go Smoothie, if I want just a touch of flavor I go with the Diamond. Hard to say either one is better than the other. The Diamond is pretty straight forward plug and play and the Smoothie has a little more tweakability. The Diamond is easier to use after dirt/od (if you are into that) whereas the Smoothie seems to play better before dirt. But I own both because they are both good, and I have a small addiction to compression. All of this is subjective and YMMV of course.
Comparing the Diamond and the Smoothie, I find the Diamond to compress/limit a little more but part of that is a mix a fair amount of dry signal in with the Smoothie. If I want fat tone I go Smoothie, if I want just a touch of flavor I go with the Diamond. Hard to say either one is better than the other. The Diamond is pretty straight forward plug and play and the Smoothie has a little more tweakability. The Diamond is easier to use after dirt/od (if you are into that) whereas the Smoothie seems to play better before dirt. But I own both because they are both good, and I have a small addiction to compression. All of this is subjective and YMMV of course.