If I could find the thread, it'd probably be helpful here where I had quite a conversation about whether to turbo the Buick and what to do. The punchline is this, turbos make hp, superchargers make torque. If you have a motor that does excellent at getting off the line but falls on its face once you're moving - turbo it. If you want torque because the motor can't get off the line but has acceptable power above - super charge it. These are GENERAL rules of thumb, both turbos and superchargers can act like the other... on my Buick, I have a 455 (now 430 ci), I traded torque for hp (okay 700 lb torque and 900 hp at race tune isn't really much of a trade - but had I supercharged it the hp and torque numbers would be almost mirrored) by going with twin turbos.
Once you decide what you want for induction, then you can talk about whether or not twin, or single - keep in mind that turbos also come in scroll, variable vane, and compound arrangements. In 99.9999% of the street cases, twin turbos are better because you get a wider range of hp and less heat. With that said, you need another engine's amount of space to package it all. Single turbos are better for packaging, but then you have to start deciding what rpm range you want your turbo to do its best (it efficiency range looks like a big tear) - the faster you spin it, the more heat it will generate - whereas the larger the turbo (less heat per rpm) the more turbo lag you'll have (this is where you talk about what the motor NA looks like).
Honestly, I don't think a turbo'd H2 would be a bad thing because it'd make the motor more efficient at highway speeds and get it to highway speeds faster. It'd do nothing but add weight, however, in off-road situations unless you went with a tiny turbo(s) for instant boost.
For this forum, a supercharger is by far and away the better choice because you have instant boost - which is what you need when you're pulling 8000 lbs up a 18% hill. On the mall thread, turbos are perfect... but that's a bit bitter - most of our rigs spend most of their time on the road - so getting better economy at speed is definitely something to consider.
For me - I have an alpha - I'd lean towards at supercharger because I think GM screwed up by not putting the 6.0 liter in the alpha - it doesn't have a lot of torque and for where I drive, torque would net me better fuel economy.
