Crown Victoria is on it's own platform and is obviously a Ford. It has a 4.6 liter V8, RWD, bench seats, etc. Basically it's a reincarnation of the 1960's family mobile but makes ideal cop cars because of size, durability and the fact that Ford discounts them up the wazoo.

The Caprice/Impala are both based off the old B-Body platform and use the 5.7 liter V8 that was LT1 based. They both handled like crap the the Impala was actually pretty cool because it had a lot of old muscle car traits such as big body, lots of power, crappy seats and no handling prowess. Impala junkies love this.

The new Impala has a 3.8 V-6 and is FWD. You can get a supercharged version now that's supposed to recall the days of the old Impalas but doesn't because GM sucks and that's pretty much a well known fact anyway. :gives: