I don't know how the unichip works, but with the AP, you can download new real-time maps and upload them etc ... I had it on my legacy and loved it .. .
If you're limiting yourself to only these two choices, it's a no-brainer decision, just go with the Cobb AP and don't look back...
I have a competitor's EMS (the Xede) that works very well for me and I don't intend to change now, but I asked (email and phone) Cobb repeatedly about the availability of the AP before I lost interest in them and bought my Xede. If I was still in the market for an EMS today and had no tuning experience, the Cobb AP is the one I would buy without a second thought.