I would say that the (original) Digitone has a specific sound which differs from Operator. In part this is def due to the effects, but also because of its simplified interface, number of operators, its filters, feedback implementation and maybe most importantly its internal oversampling:
Personally, I never really gelled with the Operator interface, although it’s obviously very powerful. It comes down to a matter of taste. I vastly prefer the sound and interface of the Digitone, but if you enjoy Operator and know how to use it well, it might be redundant.
Also check Digitone versus Ableton Live Operator.