I probably said this already, maybe in this thread lol, but:
I have a feeling that the BRZ is going to be a bit more polished, a bit better plastics, and maybe even more sound deadening. I'd love to have alcantara seats, HIDs, push start and auto climate control, but the only thing I really, really want is HIDs.
That being said, I like the styling of the FR-S better. I like the 86 boxer emblem on the fender, the tach, the front end WAY better. The BRZs gauge cluster is meh and not sporty IMO, and the silver trim is probably made of better plastics, but I don't like it. I was against buying a Scion, and still really would like an actual Toyota car, but I've gotten over that.
So assuming the FR-S is 23,000 and the starting BRZ is 25,000 I'd be buying the BRZ for just the HID's. And $2000 for HID's just isn't worth it.
In the end I'd like the amenities, but if the Scion puts a smile on my face then it doesn't matter what the inside looks like. I'll test drive both, just to make sure...
As far as the HIDs go, I'd maybe try a H9 to H11 (if applicable), an HID retrofit, or save up some money (eventually) for a pair of EU GT86 headlights.