EXS 24 Logic Sampler Users Group

You can use the Cube without the Performance Set.  The cube has the 
standard multisamples - sustains, stacattos, pizz, etc.  You can do 
pretty much anything with the Cube.  The Performance set augments it, 
you get the legato instruments, and runs and repitions, which make 
for more realistic phrases.  However, the legato tool and instruments 
(especially the legato woodwinds) are amazing - the way it connects 
the notes must be heard to be appreciated.  You just play normally 
and it switches for you to make really fluid sounding runs.  This is 
what sold me on VSL and I will never use standard samples after using 
the Performance Legatos found in the Performance Set.  

Hope that clears it up a bit.  In a perfect world, buy both.  But if 
you have other orchestral samples, definitely check out the 
Performance Set if you can only buy one.  It's really revolutionary.  

Oh, I'm basing this on the Giga version, the EXS isn't out for a few 
weeks.   Just for the record.....