I have a 2010 Nytro and Vector. From a chasis stand point they both are a ton fun and are entierly different sleds in their own way.
After riding each for a few thousand km, here is what I found:
-If you like the idea of riding standing up and stretching the legs -nytro.
-On trails that are tight, sometimes choppy with lots of sharp turns - nytro.
-For big mile trips with sweeping turns and long straights - apex.
-For longer trips and peace of mind between fuel stops - apex. [The larger tank on the apex and vector takes the edge off on long day trips, I can get about 240km on the vector from a tank. the nytro's 28l tank only gets me about 185km.]
-Top end. If you do lots of lake running - apex. [The nytro's engine is fantastic. It gets to its top end pretty quick and then flattens. If you do lots of lake running iam sure the apex would scare the bejesus out of you, where as the nytro can be put to the bar somewhat comfortablely].
-high speed runs - apex. [I have always felt better on the vector doing speed runs than the nytro. It has a lower profile, a bit wider. the nytro has such a high center of gravity].
-Agressive trail riding - nytro. [After upgrading skis, i feel way more comfortable getting aggressive on trails on the nytro. The weight of the vector and inside ski lift gets unerving on tight turning trails]
Hope that helps. I have not spent much time on an Apex but thought some the characteristics between the Vec and Nytro may assist.
MS