I owned a Parasport Italia Z1 and really liked it. The flip-up visor is a really nice feature and it is easy to use even with your gloves on. If you jump in low temperatures (like I do, I live in Finland ;) ) you must remember to check that you are able to open the visor with the gloves you are using when you skydive. Otherwise if (when) the visor gets all foggy you are in trouble...
I would recommend the Z1. It isn't known to open in flight like some of the Sky Systems helmets. It is cheaper than the Oxygen. It has two internal dytter pockets. The visor can be pulled up out of view under canopy. Only time mine ever fogged was when I blasted through 6k of moist industrial haze. I had water dripping from the helmet. It cleared almost immediately after I got out of the haze.
Myself and Merrick both have Z1's. Everyone at the DZ seems to agree that they are a really good full-face. I did some reading of the different reviews on helmets before choosing and it seemed the choice. One of the gals at my DZ that flies video said she even wishes there were some way to put her camera on hers as she prefers it over the Oxygen vid helmets by far.
I have a Z1 and love it but just ordered a oxygen video helmet which i have not received yet , While looking around i found that Pier -1 can install a aluminum video cage for the Z1 , I would be interested in to hear from someone that has installed one.