I'm not aware of any future plans to upgrade Kauai's TRS to P25 (Phase I or II) so my guess is you'd be safe with the HomePatrol 1 for now. Either will work, it's just a matter of what you'll be able to hear. As time moves forward the trend it moving everything to P25 Phase I or II like the statewide HIRIN TRS.
Major differences between the two radios is Home Patrol 2 can receive Phase II P25 and Home Patrol 1 can only receive Phase I. So the only Digital I am aware of on Kauai are EMS. Police Fire and Ocean Safety are still on the Analog TRS.
Might want to consider the Uniden BCD325P2 - it has Phase II capability and is about the same price as the HomePatrol, just doesn't have the full database preinstalled...you'll have to use Software to program it.
Happy Scanning,
Aloha!