Bigger calipers = better braking?
Discussion
Ive not seen any tests, but doubtful that braking distances decrease because of a caliper change. Usually you need more grip from sticky tyres first. The standard setup can reach the limits of the OE tyres
the change could have been for reasons, product ranges of supplier move on and manufacturers have to stay with something that's available ... the earlier calipers have been in use for 13 years or more....
the change could have been for reasons, product ranges of supplier move on and manufacturers have to stay with something that's available ... the earlier calipers have been in use for 13 years or more....
I assume you are refering to the factory 12.25MY changes, which included the bigger (lighter) 380mm (+25mm) front discs and 6-piston calipers from the V8S, alongside wider higher grip tyres? If so then they certainly do offer enhanced stopping power! Note there were a good number of other changes applied (e.g. more direct steering, cosmetic/aerodynamic tweaks and a much higher standard specification in the US). 
Braking distances in normal operation are limited by the combination of tyre grip and vehicle weight, so fitting Boeing 747 calipers will not help because once the tyres start to lose grip, then the braking limit has been reached. If you can lock the wheels in braking, or activate the ABS, then the limit has been achieved.
Installing bigger calipers and discs will need to be combined with a different master cylinder otherwise the higher fluid volume required to operate them will give a "spongier" feel to the pedal, so these changes are also normally combined with a different servo assistance ratio also.
Bigger brakes will assist with braking efficiency on a car used more to the limit as the thermal load build-up is spread over a greater area, aiding cooling through convection and reducing any likelihood of overheating and fading. The pads also operate further from the centre of rotation so their leverage ratio is increased and improved. The problem with increasing size is the increasing disc and caliper weight which can then mean the expense of hybrid or Carbon Ceramic discs and lightweight calipers.
The larger calipers also mean multiple pistons to operate wider pads, again increasing cooling, reducing the brake fluid temperature build up through conduction in the pads, and the wider pads can use staggered size pistons to maintain an even clamping force on the entire width of the pad.
Installing bigger calipers and discs will need to be combined with a different master cylinder otherwise the higher fluid volume required to operate them will give a "spongier" feel to the pedal, so these changes are also normally combined with a different servo assistance ratio also.
Bigger brakes will assist with braking efficiency on a car used more to the limit as the thermal load build-up is spread over a greater area, aiding cooling through convection and reducing any likelihood of overheating and fading. The pads also operate further from the centre of rotation so their leverage ratio is increased and improved. The problem with increasing size is the increasing disc and caliper weight which can then mean the expense of hybrid or Carbon Ceramic discs and lightweight calipers.
The larger calipers also mean multiple pistons to operate wider pads, again increasing cooling, reducing the brake fluid temperature build up through conduction in the pads, and the wider pads can use staggered size pistons to maintain an even clamping force on the entire width of the pad.
8tech is right in the booster ratio change, but the master cylinder has stayed the same throughout the DB9/Vantage/Rapide/Vanquish models.
Another thing to consider is the fluid volume is taken into account when tuning the DSC system, you may not notice a difference but the system may not work correctly if you increase the caliper piston sizes, especially if you get into a situation where it needs to apply brake pressure to a wheel.
Pre VH212.25 also used the older ABS module and Active Booster, they were subsequently updated to V8S versions at the VH212.25 change.
Another thing to consider is the fluid volume is taken into account when tuning the DSC system, you may not notice a difference but the system may not work correctly if you increase the caliper piston sizes, especially if you get into a situation where it needs to apply brake pressure to a wheel.
Pre VH212.25 also used the older ABS module and Active Booster, they were subsequently updated to V8S versions at the VH212.25 change.
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