Besides trim package(i.e. interior material/Full Bucket seats vs bench/60-40 split/and exterior chrome/black out with door spears/rims & tires/etc.)
The Impala's and Caprices varied with suspension and brake packages
Impala/Caprice some 9c'1/Special Ordered Caprice's came with four wheel disc brakes
Impala/9c-1's/9c-6's all shared the "Heavy-Duty" suspension
9c-1's/9c-6's came with a "Heavy Duty" reinforced frame with extra(s) body mounts/bushings for extra dampening
9c-1's/9c-6's came with "heavy duty" shocks
Impala's got the Sport version of the "heavy duty" shocks
9c-1's/9c-6's came with taller than stock "heavy duty" springs
Impala's got the lower than stock "heavy duty" springs
9c-'s/9c-6's/Civi Caprices came standard with the 4.3L L-99 V-8 with single outlet exhuast in '94-'96 with the 5.7L LT-1 with dual exhaust being optional
Impala's came with the 5.7L LT-1 with dual exhuast standard with no other engine offers
That's the basics with many other options for the various levels/packages..
The options codes and info can be found here
Oh and can't remember exactly the year('94/96??) but Chevrolet designated all Caprices "Caprice Classic" reguardless of the trim they were ordered with..