I Guess the cords or layers on material could be separating. I don't really go for Firestones myself; thats just the stuff the manufacturer got a deal on to put on the car when it rolls off assembly.
Personally, I prefer Falken, Bridgestone or Hoosier tires depending on the application(performance-wise.) For good, long wearing, reliable, reasonably priced tires for your regular vehicle....a set of Coopers are a safe, economical decision. Cooper does have performance line as well.
Figure out exactly what you want from the tires first. Prioritize performance, useage, wear, price, etc. Then go to a web search for tire reviews and comparisons, and match up your needs to what they present to you. I wouldn't bother asking the tire guys and the tire places, because they are just going to sell you what they got based on the same info.