Not sure there’s any specific software for just psy or trance … normally a DAW (digital audio workstation) will be used for every style imaginable. It’s all what sounds you use and how you put them together that makes the style. Some synths/effects will however have more of the right sound for psy then others. I think most of really good psytrance is made predominantly on hardware though. This doesn’t mean to say you can’t make some bloody good psy on just software.

I personally use cubase 6.5 to make music (+a shit ton of vst instruments/effects) … this ranges from psy to drum and bass … from chillout to hardcore.

Another program you might want to consider is Ableton. Cubase and Ableton are pretty much the top two contenders for making any kind of music.