The top one. It is theoretically possible in AU SDK, but it's been utilized like 1 out of 1000 times.
http://www.rawmaterialsoftware.com/view ... f=8&t=9523That link will be of no help to the specific topic at hand (Ren+ "x" DAW), but it's a quick glance at what developers have to deal with to get MIDI Out working like a VST in an AU. Many just give up and bundle a VST version and note in the manual "want MIDI Out, use the VST version).
Again it's coders going back forth but the first few posts are easy to see what the conversation is about. One poster from Arturia even mentions how they had to use the IAC "behind the scenes" to get the MIDI out working. I guess you might call that the "rich man's version of the 'poor man's IAC" workarounds many Ren users have been exploring and utilizing.
So long story short MIDI out in AU is possible in the AU SDK but a bit of a pain to implement from a coding standpoint.
I think after the next couple updates they really need to consider a dedicated controller mode like Maschine. It's such a simple solution to so many MIDI headaches when using something like the Ren/Studio or Maschine in a DAW.
I imagine they might be afraid it would cut into MPD sales, but I don't really think it would hurt those sales at all, given the huge price margin with MPDS being a $100-$250 thing and the Ren over a $1000. So while the general audience is the same it's different economies and user needs, so they may as well do a controller mode. It would just be another good selling point, and one more thing it's matched Maschine on.