Actually, apologies for being sloppy on this one (in having dashed this off in just a few minutes) - under tax laws, you can't have an ISO without a 90-day tail. This should therefore read "4) NQO without 90 day tail on termination". I would probably put ISO with 90-day tail and no early exercise as #5. It really is a toss-up, though, because the ISO does retain significant tax advantages for anyone who can keep his option exercises out of AMT. I give the NQO (with no tail) the edge here only if AMT becomes a factor, which it does for many people, primarily because it gives you have the flexibility to keep vested options alive long after leaving your employment. Hope this helps.
You mention the preference order as:
1) unrestricted grants
2) restricted stock at a cheap price with a timely 83(b) election
3) ISO, with low strike price and early exercise
4) ISO or NQO without 90 day tail on termination
5) RSUs
How do ISOs with a 90-day tail on termination compare? If I understand correctly, those are the most common.