First off, this is going to cost a fair bit of money to do. If you go with either Traktor or Serato, you need to buy one of their official soundcard. Serato’s base level box costs $500 in the US. If you really want more outputs though, you’ll need one of the more expensive cards. Native Instruments gets you more bang for your buck in the soundcard department, however it does not have the integration with Live that Serato has. Plus, you will most likely want to buy another turntable. Also, to truly take advantage of using a DVS AND Live, you’re going to need a mixer with more channels.
Okay, so let’s say you do decide to commit to this. You have two options. The first is Serato with its native LIVE integration. From what I’ve seen, the integration is very good. It’s like the two programs just magically melted together. I used Serato for many years before switching to Traktor. If you want a solid DVS, it works brilliantly. Your section option is to use Traktor and LIVE. There is no official integration between the two. Here’s where it gets tricky. You could do two things here. The first is to simply sync the midi clocks of both programs. The problem here is that you cannot have both programs in full view at the same time unless you use a dual monitor setup. You can then choose to mix directly in your mixer or route the audio back into LIVE and be able to add effects to the traktor audio coming in. Once again, you’re going to need a larger mixer if you want to do this. You can also run into latency and sync issues.
Finally, no matter which way you go, you’re going to want a new controller (or 2). Midi keyboards are great for producing, but not so great for programs like Serato or Traktor.