Latency, latency, latency.
Try basing your soundcard choice on whatever provides the most power at the lowest latency. Particularly for live play. If you can't get a reliable 2-3ms out of your soundcard for as many voices and sounds that you actually want, you aren't getting the equivalent of REAL hardware, nowadays.
There's a 'connectedness' to the sound that latencies higher than this just don't give you. It can really mess with your sense of 'pocket', and that tactile feeling of actually hitting something real, rather than a 'simulation'.
I'm not sure about the 'Dark Side' of the force, but I believe I've heard that RME interfaces can get pretty damn low and still stay stable (say that three times fast!) for Windows computers...
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An arranger is just a tool. What matters is what you build with it..!