[skorpioskorpio]

Turbochargers and superchargers produce power in different parts of the RPM range.

Turbochargers require the engine be passing a fair bit of air already to get spinning (AKA: turbo lag) so they make their boost more in the higher RPM ranges. Before fuel injection it used to be even worse since typical applications usually put the carb either at the beginning of a really long intake plenum or sitting on top of a thousand degree heat source. Turbo lag can be reduced with a smaller turbo that gets spinning faster (but produces less ultimate boost). There are also dual stage systems that use a smaller turbo and a larger turbo driven of a common exhaust plenum. There is also variable vane turbos that can be electronically controlled to produce varying boost. Turbos also add more heat to the intake gas mixture which is where intercoolers come in to cool this gas mixture between the heat source and the intake. Oh and then there is wastegates to bleed off over pressure. It can all get pretty complicated.

Superchargers are basically just a belt driven pump, though these can come in several different configurations from the familiar Roots type you see on top fuelers (which is really a part borrowed from a 2 stroke diesel engine) to centrifugals which look like just the compressor side of a turbo with a belt where the turbine would usually be (there are also screw types and progressive vane types). The power is more linear and at modest boost levels will act, for the most part, like an engine with larger displacement and higher compression through out the RPM range. It'll consume more fuel, be more prone to pinging and pretty much have all the issues a higher compression higher displacement engine will have but without the benefit of component parts of a larger engine, add to that that the blower will also add additional stress on the rotating assembly of the engine to drive the resistance of the compressor. At higher boost levels, and at higher rpm ranges the intake pressure can start to do funky things to everything like blowing the intake valves open (when they aren't supposed to be open) or creating so much back pressure that turning the blower (especially in the case of positive displacement roots and screw type blowers) becomes very difficult. Positive displacement blowers also are designed to not allow any back flow at all or any forward flow if not driven. Unlike turbos superchargers do not typically have the equivalent of a wastegate to limit pressure so are typically driven (by varying the pulley size or actual pump size) to achieve a fixed target boost level.

Both superchargers and turbochargers increase the baseline pressure of the fuel/air mixture so that the engine is compressing a pre pressurized mix. They will both increase the stress on the combustion chamber related components, both be more prone to knock and both will push components past their design limits. To say that turbos are free horsepower is not exactly true, they create a lot of exhaust back pressure, introduce all kinds of heat to the intake, basically make all the typical things you would do to a normally aspirated engine to gain a little bit of horsepower a lot worse, like adding headers to make the exhaust evacuation more efficient, or adding a cool air intake.

Both have their place in both low additional horsepower and high, and both can be made to be drivable and dependable, and both can be made to disintegrate an engine. At the dependable and drivable levels turbos can be more dramatic in that you hit a certain RPM range and all a sudden it's like you kicked in an extra engine, where the supercharger being more linear doesn't have that tipping point where it's like you flipped the "more" switch. Also superchargers will consume fuel like a larger engine all the time.