I have barely even held a phantom, but I thought the material on the phantom was good quality. The webbing strength is similar to that in any other saddle, which is really what is holding your weight. I cannot attest to the comfort of the phantom but it seems well built, like Aerohunter and most other products out there. Aerohunter definitely builds their saddle with more robust waist and leg buckles, if that is a concern.
There are some pros and cons to each. The adjustable bridge on the Phantom seems easier to use than the flex bridges, but I rarely adjust a bridge once it is set. The comfort channels are a neat concept, but most people will likely run them in the middle channel most of the time. On the other hand, the pleat on the flex does allow some adjustability in the size of the seat, but it can slip after an hour or so, opening fully.
I have found a lot of comfort with the flex. I am sure the phantom will be comfortable as well.
It is hard to know exactly what you want when you can't go to a store and try them on.