The independent evaluation shows that the Samsung Galaxy S4 offers more than 1,000 minutes of talk time and 400 minutes of Internet use on a single charge.
With regards to processor oomph, the Galaxy S4 is also pick of the litter, with its 1.9GHz quad-core chipset posting a Geekbench 2 score of 3188, comfortably ahead of both the HTC One on 2798 and the Sony Xperia Z on 2173.
Android enthusiasts will be all-the-more chuffed to discover that the Apple iPhone 5 came near the bottom of both rounds of testing, offering just 500 minutes of call time and posting a meagre benchmark of 1664.
"We put all the handsets through the same tests. Undoubtedly, Apple will upgrade its next iPhone when it launches this autumn. For the moment, Samsung's Galaxy S4 is the phone to beat when it comes to speed," Which? noted.
In fact, only the Nokia Lumia 920 was discovered to have a worse battery life than the iPhone 5, offering users only 235 minutes of Internet use - an interesting result given that the Lumia 920 packs a reasonably hefty-sounding 2,000mAh battery compared to the iPhone's more modest 1,440mAh battery.
Another intriguing finding was the lack of correlation between strong battery life on calls and good battery life for Internet use. For instance, the Xperia Z offers the second-best call time on 985 minutes, but only the fourth-best amount of Internet time at 332 minutes. The reverse is true of the HTC One, which was found to have the second-best battery for Internet use (339 minutes) but ranked fourth for call time (771 minutes).