There are three routing for MSP-KOA on NW:

1) MSP-HNL on A330, HNL-KOA on HA.
2) MSP-SEA on 757, SEA-OGG/KOA on 757.
3) MSP-(SEA/SFO/LAX/PDX) on 757, (SSLP)-HNL on 757, HNL-KOA on HA.

1: Most preferred travel method and best seat option. With WBC seating on the 330-300 series, you get the most comfortable seats, although upgrade on MSP HNL can be difficult. As Interisland portion is on HA, checking nwa.com for online availability may not be possible. You'll likely resort to calling for this option.

2: Not desirable but easiest to search nwa.com. As FC is the 757-300 version, its seats are not as comfortable as the A330 WBC seats. I wouldn't recommend it. Connection in SEA, then a stop in Maui where they refuel and clean aircraft before departing for KOA is also a bother.

3: Worst case scenario. Choose this option as a last resort. Double connection AND the 757 FC on NW metal. As Interisland portion is on HA, checking nwa.com for online availability may not be possible. You'll likely resort to calling for this option.

Jiburi