We tested both kits. The Volant added 8-10hp at around 5000 RPM, and the aFe added about the same around 4500 RPM.
As someone has said, dyno tests are a little sketchy and somewhat imprecise. Both aFe and Volant claimed HP increases around 20hp.
There is a benefit to adding a cold air intake at lower RPMS - it's just hard to measure. Doing a dyno test in first or second gear is difficult and inconsistent, so most testers don't bother. However, it stands to reason that there must be some benefit. I've never tested in 2nd, but we've ran tests in 3rd and seen 5 hp gains on both kits (we didn't display these results because they weren't that exciting).
aFe test -
aFe Air Intake Toyota Tundra Review with Video Sound Clips | tundraheadquarters.com
Volant test -
Volant Cold Air Intake Toyota Tundra Product Review with Video and Sound | tundraheadquarters.com