Consumer Reports tested the Verizon iPhone 4 using the same methodology as the original GSM version, and with the same results: signal strength drops if the iPhone 4 is gripped in a certain fashion, commonly known as the "death grip." As a result of its testing, Consumer Reports decided it couldn't recommend the Verizon iPhone 4, either.
Similar testing done by AnandTech throws some cold water on Consumer Reports' findings, however. Not long after the Verizon iPhone 4's launch, AnandTech found the Verizon iPhone 4's "death grip is essentially mitigated."
The Verizon iPhone 4 experienced a signal loss of 16.5 decibels (dB) when held in "death grip," compared to signal loss of 15.5 dB when held "naturally." This is far better performance than the GSM iPhone, which experienced signal loss of 24.6 dB in "death grip" and 19.8 dB in "natural grip." In other words, the Verizon iPhone 4 in "death grip" mode experiences less signal degradation than a GSM iPhone 4 held "naturally."