Dunno about that version of the crux thing - its suffering rather from gram shaving one way then putting it back on with zipped pockets etc.
There's a reason that PHD keep the 900 FP down for the ultra vest/pullover
(iirc only ~20g of the weight difference from the minimus is down.). Mind, that pocketless pullover one they've got seems entirely sensible.
As for the Nitro vs minimus, I'd be surprised if there was a big warmth difference either way. Maybe minimus slightly warmer - after all there have been magazine reviews putting it ball park equal to the anti freeze.
One thing I am sure about is that you'd need heat pad/mannequin testing to be at all confident. The BPL testing didn't find a great link for anything else. And yes fit will make a non trivial difference to heat retention!
Edited: 24/01/2012 at 23:18