The 747-400 WABC (Weight And Balance Computer) was allegedly not accurate enough and in the company I flew them for, only used for a gross error check as well, like SMOC's compant (may be the same one). The company preferred us to use the loadsheet figures - the cynic in me suspects this directive came from the accountants!
When you saw an aircraft loaded full with passengers who were last at the notional weight when they were considerably younger and their '7kg' of (unweighed) cabin baggage, I was more inclined to belive the WABCs were more accurate than the loadsheet, as I never saw a WABC MTOW that was below the loadsheet figure. Some differences were truely staggering and lead to the addtion of a few knots for good measure.
The A320 series actual mass can be found in the AIDS in the Alpha codes if your company's aircraft has the option. The codes are GWFK for kg, or GWFP for lbs. I always check it if flying an A321, because the aircraft always believe they are a bit heavier than the loadsheet. The AoA probes feed their information into the FACs (Flight Augmentation Computers) which in turn compute the safety speeds including VLS (Velocity Lowest Selectable), However, the VApp is computed from the FMGC's (Flight Guidance Management Computer) weight that is input during initialisation from the loadsheet weights. This often gives less than the required 5 knots difference required, so I input an increased VApp based on 1 knot per tonne increase over the loadsheet weight. The aircraft is more flyable and manageable with the increased VApp, so I suspect the FACs are probably correct.