Damien, what sorts of software features are you looking for? Consider at least the following questions:
What kind of music do you play most often? Does it vary substantially in BPM range? Do you play only music that is just electronic 4×4, or do you play old (or current) songs with live drumming (and\or other percussion, such as Latin or African), or with different time signatures, or electronic music with a “swing” built into its arrangement?
Are you interested in doing live remixing with remix decks or stems, or would you be interested in editing your songs before your performances (whether using a sound app like Audacity or a full-blown DAW), or doing it using within your DJing software itself, whether before the performance or right on the spot?
Do you prefer to have the screens or panes representing each deck (song) separate from each other, or would you prefer to have the app display the moving waveforms in a parallel format, next to each other, whether flowing vertically or horizontally, and have the option to switch views during performance?
Would you be play and mix, now or in the foreseeable future, also music videos (be a video DJ, too).
After going through questions like this I chose Serato, but only after first using djay on an iPad and a Numark iDJ Pro and sometimes Traktor for a few months.
<However>, there’re many valid reasons for choosing Traktor, or Cross, VDJ, Djay Pro, the new Rekordbox 4.0, as well as Ableton Live or even Apple’s Mainstage (the live-performance sibling of Logic Pro X).
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