Tell us a little more about where you are going to run it and what your experience with RC is. These are really different trucks, made for different driving conditions, so it depends on what you plan to do with it.
I have a Kraton, Outcast, and I have a Nero that I just received so I only have about 15 minutes of run time on the Nero. I run on grass, I have a couple acres, and farm field mainly, very rarely on concrete or asphalt. Based on that experience I would say;
* Kraton - if you want to Jump and go ridiculously fast on uneven grass, dirt, farm fields this is it. No comparison to jumping this to the heavier Nero/ Fazon.
* Nero/ Fazon - (Nero and Fazon are the same basic car, just some small tweaks) Lots of fun on grass/ dirt. Donuts and rooster tails galore and really a fun truck to drive, the weight seems to allow it to flow over uneven surfaces better than the Kraton. If you are driving on flat areas this seems ridiculously fun, it grabs when it needs to but it will spin in a full circle at will when its in the right mode. The ability to switch modes is something that I bought it for, with only 15 minutes of drive time I can say that each mode definitely makes the truck different.