Update Sept. 28: We've updated this story with a new battery result for the older iPhone X and additional context around Apple's iPhone XS battery life claims.

If you really care about battery life and you're in the market for a new iPhone, we would opt for the iPhone XS Max over the iPhone XS. Apple's 6.5-inch flagship lasted nearly an hour longer on a charge than its smaller, 5.8-inch sibling.

On the fence between Android and iOS? You can get considerably better endurance from Android phones, especially those with larger batteries.

iPhone XS and iPhone XS Max: Their Battery Life vs. Competition's

Phone Battery Life (Hours: Minutes) iPhone XS Max 10:38 iPhone XS 9:41 iPhone X

9:51

Huawei P20 Pro 14:13 Google Pixel 2 XL 12:09 Galaxy Note 9 11:16 OnePlus 6 10:33 Smartphone Average 9:48 HTC U12+ 9:13 LG G7 ThinQ 8:35

We put the iPhone XS and XS Max through the Tom's Guide Battery Test, which involves continuous web surfing at 150 nits of screen brightness. For this test, we turn Auto-Brightness off and True Tone off in the display settings.

To ensure consistency, we run all of our phone battery tests on T-Mobile's network, and we ensure that the phones have full signal strength by using a signal booster called the T-Mobile 4G LTE CellSpot. In other words, this is as close to ideal conditions as we can get while keeping everything repeatable.

The iPhone XS Max turned in a run time of 10 hours and 38 minutes, which is well above the smartphone category average of 9:48. However, the iPhone XS lasted for just 9:41, which is slightly below the average.

Last year's iPhone X lasted 10:49 on the same test, despite claims from Apple that the iPhone XS was supposed to last 30 minutes longer. However, that claim is based not on web surfing but a mix of real-world activities a given user might do throughout the day.

Interestingly, when we ran the older iPhone X through our battery test again, it achieved a runtime of 9 hours and 51 minutes. That's still better than this year's iPhone XS, but not by much.

MORE: Smartphones with the Longest Battery Life

Why the big drop year over year? Part of it could be the age of the phone, but the battery capacity said 100 percent in the battery health settings of the handset. It could be that the same websites we used in last year's test have injected more Javascript and other code on their pages, which could place more stress on the phones.

Both new iPhones beat certain Android phones, such as the HTC U12+ (9:13) and LG G7 ThinQ (8:35), but they were outclassed by other Android flagships in this category.

Google's Pixel 2, for example, lasted 12 hours and 9 minutes on our test, while the Huawei P20 Pro endured for more than 14 hours. The Galaxy Note 9, which packs a 4,000-mAh battery, lasted a very good 11:16, which is nearly 40 minutes longer than the iPhone XS Max lasted.

Based on a recent teardown, the iPhone XS has a relatively small battery compared to most Android phones, at 2,659 mAh, which is smaller than the 2,716-mAh battery in last year's iPhone X. The iPhone XS reportedly packs a beefier, 3,179-mAh battery, but that's still less than what most Android flagships have, ranging from 3,500 to 4,000 mAh.

To be fair, the size of the battery is only one factor in a phone's battery life. The software, processor and other aspects also come into play. In fact, the 7-nanometer A12 Bionic chip in the new iPhones has four efficiency cores that are designed to be up to 50 percent more efficient than the A11 Bionic.

But based on our results, the iPhone XS and iPhone XS Max don't have the staying power of the best Android phones when it comes to our web surfing test.

Credit: Tom's Guide