depends on how much you ride switch really...
there are plenty of great non-symmetrical twins out there, as well of symmetrical ones. you may notice a slight difference in the fluidity of riding switch.
a lot of people seem to forget that while symmetrical twins make riding switch better, you also lose a little performance in your traditional riding. so choose wisely. if you spend majority of your time in the park and arent concerned with performance in and out of the turn, go symmetrical. if youre a 50/50 guy, go directional (non-symmetrical)