I watched one of the Son of Sam investigators on the tube last night. He said the difference between the two cases was that Berkowitz's murders were spread out over months--over a year, as I remember--and these murders have happened within days, if not hours.
He didn't mention it, but the Son of Sam case was solved because of tedious police work and lots of shoe leather--Berkowitz had gotten a parking ticket in an area near one of the murders and the job of one of the investigators was to check out all the people who'd gotten tickets. It's going to take one of those kind of breaks to solve the case.
It is different from previous cases in that so many victims have been killed in so few days. Read in USA Today the difference between serial killers and spree killers is that serial killers target their victims and they have something in common - i.e., target all women, or all blonds, etc. Spree killers will kill anyone for the thrill. Guess that means this is either a thrill killer or somene with an agenda to send a message to America.