Numbers don't lie, but sometimes they don't tell the whole story.

On paper, the GMC Sierra Heavy Duty pickup with its 6.6L, direct-injected V-8 Duramax turbodiesel is the clear-cut power champ among the Best Engines Diesel Shootout trio Ward's pitted head-to-head.

Its 397-hp and 765-lb.-ft. (1,037-Nm) torque ratings easily outdistance the 350-hp/650-lb.-ft. (881-Nm) output of the Ram's 6.7L I-6 Cummins Inc. diesel.

They also narrowly top the 390-hp/735-lb.-ft. (997-Nm) peaks of the Ford Super Duty tested. To see if the Sierra had superior off-the-line acceleration, we took to the back-straight of the 1.3-mile (2.0 km) Robert Bosch LLC proving grounds for a series of 0-60 mph (97 km/h) runs.

Two sets of tests were conducted, with and without trailers attached, using a speed gun and special computer software (courtesy of our colleagues at Motor Trend).

In the towing test, identical 10,000-lb. (4,536-kg) trailers were pulled with their foldable flaps in the up position. Measuring 6-ft. (1.8-m) wide and 4-ft.-8-ins. (1.4-m) tall, the flap simulates the type of speed-curbing wind resistance that could be expected when pulling a boxy camper 8-ft.-5-ins. (2.6-m) tall.

In each case, the trucks carried four occupants, driver included. Three runs were made per test, with only the best times used for comparison purposes.

And the Sierra came out on top.

With trailer in tow, the Sierra nosed out the Super Duty by 0.17 seconds to 30 mph (48 km/h) and held on by 0.13 seconds on the run up to 60 mph. The gap with the Ram was more pronounced as the Cummins engine ran out of breath.

Without trailers, the GMC and Ford trucks hit 60 mph in an impressive sub-10 seconds, almost sports coupe-like acceleration if this were still the 1980s.

But here's the twist: The Sierra didn't feel the strongest, either in our trailer-towing runs or in more general driving.

That honor goes to the Super Duty, which means sometimes perception can be more important than reality.

Credit the slight illusion to the Super Duty diesel's baritone exhaust note, reined-in noise, vibration and harshness and exceedingly smooth interface with the new 6-speed automatic transmission.

Among the NVH-quieting features are the resonators molded into the composite intake system, tuned to different sound-canceling frequencies. Two acoustic covers on the sides of the block also mitigate high-frequency noise from the injectors.

Composure counts. Sometimes it's even the deciding factor.

Acceleration Times<br /><i>(in seconds)</i>

0-30 mph/0-60 mph (without trailer)

Ford: 3.66/9.41

GM: 3.36/8.42

Ram: 3.66/10.15

0-30 mph/0-60 mph (with trailer)

Ford: 6.35/20.40

GM: 6.18/20.27

Ram: 7.16/23.99