Engine braking is rear wheel braking. Your total braking force available is limited by available traction at the rear wheel.
Therefore, you can theoretically achieve maximum rear braking with a blend of engine braking and, uh, brake braking, or you can do this by using the brake alone.
However, in a real-world maximum braking situation, it's best to pull in the clutch and use the brakes -- it's much easier to balance and modulate two relatively predictable forces (front and rear brake) rather than introducing a third force (engine braking) that changes rapidly as you slow down.
In other words, using engine braking will never slow you down any faster than using the brakes correctly. Using engine braking in a maximum braking situation introduces an element of complexity that will increase your stopping distance. Also, bear in mind that you should also be clicking down through the gears as you slow so that you're ready to accelerate again if needed; your brain already has plenty to do.
That said, engine braking is still a useful tool in certain situations. In street riding, engine braking is useful for minor speed adjustments in many situations. It's also very useful off-road, such as when descending a steep hill on a loose surface -- engine braking ensures the rear wheel will keep turning whereas using the brake could cause the wheel to lock.
2002 Suzuki DL1000 V-Strom, Dark Metallic Space Blue
1983 Suzuki GS850G, Cosmic Blue
2005 KLR685, Aztec Red - Turd II.2, the ReReTurdening
Last edited by bwringer; 09-26-2013 at 10:08 AM.