I have tried Fuji a little bit, but it's kind of a moot point now that 800Z is gone. It is quite impressive how their film handles mixed lighting. By mixed, I mean mixed fluoro + tungsten, or fluoro + daylight. Kodak films handle mixed tungsten + daylight, or straight tungsten and straight fluoro very well in my experience.
My comments on the fluoros though was made with respect to the differences in the 400 and 800 Portras. I have some shots made in the same conditions where the 800 shows the green and the 400 doesn't. I just made two test shots on each film this week to test this explicitly, but haven't gotten them developed yet.
I don't think that Portra 400 pushed is better than 800. I could see where some people might think that, but they probably think that Tri-X at 1600 is better than TMZ at 1600. Not that there is anything wrong with that, but I'm willing to have more grain for an extra stop of real speed.
In my testing, the new Portra 400 handles underexposure pretty much the same as 400NC, maybe a hair better. I have not yet tried a true push with it though, but I would think pushability is related to underexposure latitude...