I have no actual experience so far; but, my partner and I are scheduled to fly PDX - HNL; HNL - AKL in Hawaiian International Business. The return will be Fiji AKL-NAN; NAN-LAX; LAX-PDX (Delta First).
The Fiji NAN-LAX will be on brand new A350s with significantly upgraded business seats (compared to Fiji A330s). Fiji's A350 will serve both Auckland and Sydney.
I anticipate Fiji's business class experience to be superior (at least in terms of hardware) to Hawaiian's.