The angrier you get, the less restraint, ergo, the appearance of greater strength. Which would also go along with what Paul has said. One begets the other, but not an actual phsyical, increase in strength, only the "release" of what is already available.

So, the Hulk has this subconcious restraint built in because of David's aversion to actually harming anyone, but when OBJECTS are involved, all restraint (read: subconcious control) is gone!