I was right in thinking that not everybody understands how this works! Please read my post above (and I don't mean that to sound arrogant, I just want to help).
Holding the note down gives you the recorded performance at its original tempo. Playing the notes at that speed or faster lets you play at your tempo.
Obviously, you can't play slower than the recorded tempo, because the next note in the recording will play before you play yours. But you can play a lot faster, up to the point at which the notes would overlap and sound ridiculous.
I find the dynamic repetitions the most useful; the standard ones are often only subtly different from using the Alternation tool - and even that isn't always patently obvious, depending on the program and the context.
Holding the note down gives you the recorded performance at its original tempo. Playing the notes at that speed or faster lets you play at your tempo.
Obviously, you can't play slower than the recorded tempo, because the next note in the recording will play before you play yours. But you can play a lot faster, up to the point at which the notes would overlap and sound ridiculous.
I find the dynamic repetitions the most useful; the standard ones are often only subtly different from using the Alternation tool - and even that isn't always patently obvious, depending on the program and the context.