[chrisbec]

My $0.02 for turbo versus N/A engines:
The turbo will be a cool project, a lot to learn and do. Tuning it will be a lengthy venture if you do it yourself (not recommended). You can pay to have someone else do it which will defiantly save you a lot of time and will keep you from trashing the new turbo motor, but it is going to cost you. You will probably want to invest in a rebuild of that motor and install some lower CR pistons at a minimum.
Also, most turbo set-up's that I've seen require more than one round of tuning because after the first tune you realize all of the things that weren't quite perfect initially that need to be fixed. We all know the gains are huge but ask yourself if you have the time and budget for a project like that. The turbo car will be something that you are constantly tweaking and improving. If your car is a daily driver a turbo set up may not be your best choice.
The N/A stock engine route is far less of a challenge, less expensive, takes less time to complete and makes a good daily driver since the BMW reliability can be preserved. It has been done so many times that it is just about plug-and-play, but defiantly (IMO) makes for a great car when you are done. Seriously, after a 6 cyl swap with an LSD installed the car is like a completely different car that is a blast to drive. There is minimal fab work required which will save you a huge amount of time too.
I'm not partial either way and I'm always blown away with the ingenuity involved with a turbo installation and they are all different form each other. But it really comes down to what you can afford in terms of time and money.