I've had both machines before and the only advantages the Diamante has are it's brushroll and height adjustment. Lindhaus makes a very effective brushroll IMO and the X4's auto height adjustment system leaves me wanting a bit more contact with the carpet. That said the X4 is the better overall machine. It's airflow and suction are stronger, it offers hepa style bags as stock, the hose system has better reach. Bare floor cleaning as mentioned above is definitely better with the X4.
I feel like Lindhaus machines aren't terrible but they have a lot of untapped potential. Their strength is all in their powernozzle but they just lag behind on airflow and suction
