If you're just going to use your SoftStep in Standalone mode then there is no need for a virtual MIDI port; you only need one if you're using your SoftStep in Hosted mode.
As for the best one — these days I'd probably go with loopMidi — it's more up to date. I don't believe loopMIDI was around when KMI started out, so the recommendation went to MIDI Yoke. It's just kind of stayed that way in the manuals. MIDI Yoke certainly gets the job done, though.
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