Based on the German Stiftung Warentest test and it says that the Apple iPhone 4 is the biggest loser in the signal. Pointing out that the iPhone 4 antenna gap design on the side is the caused. Statistically saying, iPhone 4 loses up to 90% of signal and is prone to more dropped calls compare to other smartphones like the N97 Mini.
GSW also noted that average smartphones only loses signal up to 25% depending on the network signal strength. But the obvious is that iPhone 4 is the biggest loser in this antenna-gate wars. In short, losing big signal means more drop calls.