It really hinges on the phytochemical composition of the particular kava you're looking at, more than anything else: meaning, the different KL%, FK-B%, and other constituents, as they might be stated in a COA.
Single-cultivar kava will generally have more homogeneous batch-by-batch COAs in comparison to blends (this will similarly apply to the more macroscopic/less accurate, yet nonetheless quick-and-dirty useful, "chemotypes," as they're called).
Speaking broadly, though, Hawaiian 'awa is generally said to be subtler, and sometimes "smoother" in its effects.
(Updating this to add that too many COAs are unfortunately botched: labs often aren't switched-on re the need to, e.g., use UHPLC over HPLC, regularly calibrate instruments, achieve complete vibration isolation, etcetera. Even plagiarization happens... yikes... but wait for TKS/R&P's COAs, which will be bona fide.)