I am going with the super charger in the picture. It is based on the HPS system. HPS had trouble with tuning in the past as well as some DIY'ers that didn't install it correctly causing some blown engines. This has cuased a lot of negativity on the MB forums. They changed tuners are a couple of years ago tp top German tuner for the ECU work. The advantage to me is that the Germans have installed some V8"s in SLK's in Germany and have fixed the key start issue. Atwood is a HPS dealer but has done a lot additional developement work to really get the power up safely. One improvement is in the picture above which is a very large heat exchcanger that allows more boost.

I really liked the Tubo idea but this set up is clean, proven and doesn't require near the fabrication work of a one off turbo set up. Also the support from Atwood is very valuable to me as well. With the right mods I could get into the mid 400HP range at the wheels. One key mod will be long tube headers which add about 40hp on this set up.