The new iPhone 6 and 6 Plus may be the largest iPhones Apple has ever made, but they're also the toughest, according to SquareTrade, a gadget insurer that publishes a "breakability" index.

Having put the new iPhones through its gauntlet of durability tests this weekend, SquareTrade found that the iPhone 6 holds up impressively well in drops, spills and slips—despite the fact that the new, thinner iPhones are tougher to hold onto given their smooth edges and bigger screens.

The iPhone 6 Plus fared well, too, managing to beat out Samsung's Galaxy S5 as "the most durable phone with a screen larger than five inches." This comes as a surprise, and not only because the Galaxy S5 is known for its waterproofing, but also because hundreds have already taken to Twitter to gripe that an iPhone 6 purchase means a case purchase, too.

Read more: WSJ reviews the iPhone 6 and iPhone 6 Plus