A typical coil spring pressure plate like a Long or Borg & Beck increases pedal effort as the clutch is released. The beauty of a diaphragm is that at a certain point, the Bellville spring over-centers and pedal effort drops dramatically. This makes it easier to hold the clutch pedal in when driving on the street. This is why diaphragms are so popular.
Details
There's also much more to this area than just pressure plates and clutch discs. Proper clutch linkage adjustment and using the right parts is also a major concern. When replacing a clutch and pressure plate, always include a new bellhousing ball stud, release arm, and throwout bearing. Many enthusiasts overlook the ball stud and release arm, and major wear here can bind the linkage and cause all kinds of grief that can be difficult to spot. For example, a worn ball stud can causing binding that can ruin parts and your general disposition.
Centerforce also offers a pressure plate called the Light Metal assembly that uses a lighter aluminum pressure plate ring with a riveted steel face. This reduces the plate's weight while also using ball bearings for the Bellville spring to ride on, significantly reducing the overall effort required to compress the spring. This allows Centerforce to add static pressure without a pedal effort penalty.
Fasteners are also critical. Most companies supply new pressure plate bolts with a new clutch and pressure plate, but if not, be sure to include new bolts and always use a torque wrench to ensure proper fastener torque. And we shouldn't have to tell you to never allow the clutch disc or machined surfaces of the pressure plate or the flywheel to get oily or greasy. And always machine the flywheel surface when using a new clutch. This will ensure a proper break-in and optimal performance from your new parts.
Conclusion
In almost all cases, the clutch disc is installed with the spring hub facing the transmission.
There's at least another story just in installation tips and tricks, but if you pay attention to details, use a quality clutch alignment tool, and don't force the trans if it doesn't want to seat in the bellhousing, you should be in for a pleasant afternoon laying under your car. Also keep in mind that you will need to be easy on the clutch for the first 100 miles or so to break in the organic material. If you pull all that off, your new clutch should reward you with thousands of miles of outstanding performance.