I dont leave for a gig without my MacBook Pro and SL box. I use VDJ at some of the clubs I work at because they have it installed but I only use it for playing videos. When it comes to playing for my gigs I stick with Scratch Live. This is the most stable setup for me. I also like the fact that with the new version of Scratch Live you can maximize the amount of space for the library.
There are a lot of things to take in consideration when selecting the best program for you. I am partial to scratch live. I have been using it for the past 2 years. It is a stable system but works much better if you are on a MacBook or MacBook Pro. I have used it with a Win7 machine with just a few glitches. Never crashed just small audio glitches that are no longer an issue since I am on a MacBook Pro. If you are using a Windows machine I have heard that Traktor works well. I have used VDJ and it is a solid platform if you are going to spin music videos. If you are looking for solid performance with mp3 files take the plunge with either traktor or scratch live.