Actually that range figure for the Sejong the Great doesn't stack up too badly against both the Burke's and Kongo's and the F-100/Hobarts, all around 4500nm@18-20kt, can't find any figures for the Atago and Asahi classes. The Koreans are only fitting 88 VLS to the Batch 2 Sejongs, of which 24 are of a new larger VLS for Hypersonics currently in development. My thinking is that two Sejongs or two Burkes or two Asahi's may have been better than three Hobart batch 2s if the GOTD decided to accept the Navantia offer, I still think overall we are better off sticking with the Type 26 build.It is important to remember that if you go to SK then you will have to buy a SK product. Yards do not simply hand over designs for which they own the IP. This may mean the NZ would rely on a logistics train based overseas which may complicate issues, however, NZ are in that position now so it is really not a change fromt the current position.
Noting the critique of Osborne and VFM. The modernised yard is full digitial yard in respect of design, build and support. A digital verson of each individual ship will be produced to allow traking of equipment, maintenance and alterations which greatly assists in the operation and maintenance of each vessel. The quality of the work coming of this yard is reported as being very good.
Delays such as those with the Arafura appear to be due to a decision of the customer (Defence), and not the yard, which appears to have delayed handover and certification. I would also note that we have not seen any industrial issue at Osbourne to date which appears to be a concern with comments in this thread.
Once Osborne gets into its stride (and provided the GOTD does not harpoon the continous build phyliosphy) then there will be significant economies of scale with ongoing builds as well as an established logistics support arrangement in the immediate region (and eventually a domestic facility for producing the weapons to arm these vessels .... again provided the GOTD does not change their mind on this) . This is also important from an operation and cost perspective.
All of this may not be sufficient for NZ to see this a value for money, however, I suggest all factors should consider before writing off potential solutions. Personnally, I do not see NZ going with the Hunter as it appears to be seen as too much. I am at a loss as to what NZ may select noting the RNZN have many of the same geographical issues to address necessitating reasonable endurance (something at, or in excess of 6000nm). The Arrowhead 140 appears to be, potentially, a good fit but you will not get that built in SK.
As an aside, the Sejong the Great (noting this appears attractive to many posters) has a range of 5500 nm and a crew of 300 both of which may be a challenge in the current climate. It will be expensive to operate and arm. Just filling the VLS will cost a great deal.