So I just put on the most recent version of Bandit, and I was immediately struck by a similarity to the most recent formulation of Derby... It's crazy actually.
I went to Basenotes to see if anyone had written anything and voila--Treeman you are totally right!! These two fragrances have quite a bit in common. Above all in the opening and ONLY in the recently reformulated versions.
I think the similarities come from the combination of leather and carnation. They are both leather chypres, and the most recent version of Derby in particular has a hefty dose of carnation in the middle.
Derby is "smoother" to my nose--the leather note is more well blended into the scent, whereas it sticks out more in Bandit and is slightly dustier in this incarnation--but Bandit could even be used as a cheaper alternative in my view. They are both excellent in their most recent formulations.
Anyways, no Treeman you are not crazy!!