I would say that for a novice the AP has many more benefits an conveniences than Open Source. For the time being all he needs is a stage 1 ots map so the pro tune can wait until he gets more mods. IMO it is not worth a pro tune unless he is at least stage 2.
With the AP he gets the convenience of live monitoring, on the fly map switching, fuel economy, Flat Foot Shifting, Launch Control, live adjustment, adjust the rev warning light, and a host of other features all in one tiny convenient package.
I guess it really depends on whether he would rather have the convenience, features and plug and play nature of the AP or whether he is just looking for a no thrills solution.
If he goes with open source he would require a pro tune no matter what since this is his first experience with the STi, any stage tunes on RomRaider are complete junk, so he would have to shell out at least $500 for a pro tune right off the bat. If he wants to be able to log and monitor things He would require a lap top and a Tactrix 2.0.
It all ends up being the cost of the lap top (if he doesn't have one) and $170 for the Tactrix plus the pro tune. With the AP it is just the cost of the AP for now. The Maps are included and they have been developed by professionals and tested by millions.
My recommendation to the OP is that he get rid of the CAI and BOV and buy an AP and go Stage 1 for now. I think the price for that is currently $595. The CIA is doing absolutely nothing for you right now. Trust me your car will thank you and reward you with good reliable power. Then when you add a down pipe you can go stage 2 and then you will benefit from a pro tune when you add even more mods.