The only reason to get a SVT Focus engine is for bragging rights. Yes, a SVT Focus engine will do 40 more HP than a stock Zetec, but it will not hold any more boost than a stock block Zetec. While the SVT is overall a better engine, the higher compression makes anykind of FI less than ideal and you will not gain any significant HP over a stock Zetec. For the cost of a new SVT engine you can buy a used stock zetec and make the bottom end bullit proof with forged internals, and still have a few bucks left over.
Now for the whole Superchargers vs Turbo's thing. The only thing a supercharger will give you over a turbo is easier CARB compliance as no exhaust components need to be touched to install one. A supercharger, will give you NO TORQUE compared to a turbo at the same boost. A supercharger also has MORE LAG, than the ONLY turbo kit for the SVT Zetec, Focus-power.com's kit. It costs more than any supercharger, but it's the only proven turbo kit for the zetec out there.
Here's a link to a similar discussion in the Cougar forums. A guy sold his Cougar and bought a SVT Focus and wanted some opinions on how to FI his SVT.
http://www.fastcougar.com/forums/messageview.cfm?catid=63&threadid=91001 
