Probably the biggest difference you will notice on a day to day basis is FMS1 on the older aircraft and FMS2 on the newer aircraft.
FMS2 has many improvements. It's much easier entering in the initial route as you just have to enter the airways and it will figure out the waypoints.
The way the system works out the optimum level is much improved as you can enter in a range of cruise winds for various levels instead of just a single level.
Another nice improvement, is that you can go direct to a waypoint on a specific radial. Particularly useful if you a doing a visual approach from a fair distance out, as you can use it to draw an extended centerline.
The bigger LCD screens are much nicer to work with than the old CRT ones. And the flight deck noise is considerably reduced in newer aircraft.
Older A/C have a cluster of separate 'clockwork' standby instruments while the newer ones have a single PFD style standby instrument.
In the older aircraft the RAT stalls at 140kts and disconnects with gear down leaving you on battery power only (!)