Ableton/Traktor: Separate or shared souncard?

Hello,
My name is Philippe and I need an advice.

I use Traktor and Ableton simulteanously when Djing.
I want to use 4 decks on Traktor (means 4 stereo channel out) and I'd like to use the preview feature , expecting to win time to control or select next track to put in the mix (mean one phones out) .

For Ableton, I want to use it with 1 stereo channel out for the main mix, 1 stereo channel for effect return.
Need also 2 stereo line 1 (1 for mix recording from the mixer, 1 from effect send from the mixer).
What do you thing is the best solution beetween:
1 soundcard for Traktor (like NI Audio8, RME or others) and another one for Ableton (NI Audio 4 or 6, Rme, or others

OR

Only one soundcard with enough line outs (6 stéréo channel out and 1 phone out) shared by both software.
No problem of USB port availables onthe computer.
Soundcard is going out &in to XONE62 A&H

What is the best solution regarding perforrmances, stability, ability to share (or not) , latency

Thank you by advcne guys to give me you point of view and experiences.

Phil