For a generic response to differences between symmetrics and asymmetrics, read this link about halfway down: http://www.bowlingthismonth.com/bowling-balls/

In regards to Track balls: A lot of symmetric balls have some asymmetry to them.  Track's "asymmetric cores" do not meet the asymmetric standard per the USBC.  The USBC rule is any ball with an intermediate differential > .010" must be marked with a mass bias.  A lot of Track's asymmetric balls have int diffs < .10" - which makes them weak asymmetrics (I.E. 607A SE with an int diff of .007").  Track does not have to mark the mass bias, but they choose to. 

FWIW, I loved the 607 and wish Track still made it.

So the intermediate differential is what makes one core stronger than the other?

If you notice all of tracks low end "assyms" are all in a line because they are simply marking the virtual mass bias..

Typically u will see variation with a true assymertical core.

The kinetic pearl (pre 505A?) Was extremely good, I think about going back to EBI one day as a customer just to throw that core again.  But then they got rid of hickland, they forever lost me as a customer. 

Symmetric balls give the maximum amount of track flare(axis migration) when the pin is placed 3 3/8' from the PAP, and the amount of track flare decreases when the pin is placed more than 3 3/8' or lesss than 3 3/8' from the PAP.  Assymetric balls give the maximum amount of track flare when the pin is placed 3 3/8' inches or more from the PAP, and the amount decreases when the pin is placed less than 3 3/8' inches from the PAP.  This allows high rev players to place the pin 5 or 6 inches from the PAP on assymetric balls to cut down on revs for more control but still maintain a high amount of track flare for more hook and less oil carrydown.