1. I own NUC6i5SYH almost one year. The WHEA error caused by wrong initialization of voltage regulator circuitry was solved long time ago (see the Release Notes for BIOS ver 0042: https://downloadmirror.intel.com/25913/eng/SY_0042_ReleaseNotes.pdf ). Today we are working in BIOS ver 0057. In my opinion this product is very mature and also other bugs were discovered and solved.
2. It shall be your decision if you should wait for NUC7i5xxx
Hope this will answer your question
This message was posted on behalf of Intel Corporation
As mentioned before, this was addressed with BIOS 0042 ever since this fix was released the reports for this error have been almost null.
Hope this information helps in your choice.
Leon and Scott, thank your for you help.