Which smartphone would you bring to a deserted island? That's a good question to ask when it comes to the new crop of high-end devices, especially if the island is not that deserted and has a coffee shop, an airport, and maybe a place to make a few phone calls.

The new Apple iPhone 6, which has a 4.7-inch screen and is about a finger-width taller than the older iPhone 5S, is a good choice for business users. The bigger iPhone 6 Plus is a bit more of an "entertainment" phone, with a 5.5-inch screen that's more ideal for watching movies (it tends to last longer due to a bigger battery). Yet both phones are facing even stiffer competition than the iPhone 5S did a year ago. It's more important than ever to know what you are missing for business features on Android and Windows smartphones like the Samsung Galaxy Alpha and the Nokia Lumia 635.

Let's start with the basics. The most important new business feature is called Apple Pay, and you may have already heard too much about this upstart payment method. On a business trip, you'll be able to take out your phone, hold the device onto a terminal, touch the fingerprint reader, and pay for a sandwich or your hotel bill. The iPhone 5S already had a fingerprint reader, but the iPhone 6 has a new NFC (near-field communication) transmitter that passes credit card data with a tap. The feature has been around for a while on Android phones but hasn't really taken over the retail world.

It's hard to say at this point if Apple Pay will add value to the iPhone 6 for business use, because it's not quite available yet. There's no way to know if it will work reliably, securely, or in a user-friendly way, and no way to know if it will be widely adopted.

The phone does use a faster A8 chip, and in my tests, most apps like Evernote, Skype, and Sprout Social did seem to run faster. They popped up on the screen and never paused if I had too many other apps running at the same time. My only issue here is that each new iPhone always runs a little faster, but in my day-to-day use running a mobile browser, checking email, and looking up flights and traffic, it runs about the same as an iPhone 5S. I wouldn't recommend upgrading your smartphone just so you can check email a hair faster.

It's worth mentioning that the iPhone 6 also runs the new iOS 8 mobile operating system (which you can install on an iPhone 5S as well), and one of the key features has to do with iCloud. It's baked into the OS in a way that makes it easier to sync your documents, contacts, and other data on the phone to the Apple iCloud.com service and then between phones and the iPad or a computer. I've heard of many small businesses that rely on this functionality quite heavily for all employees to share documents and contacts in particular. At your computer (PC or Mac), you can then retrieve them from the cloud.

In my testing, the features that helped the most during my workday had nothing to do with the new OS, Apple Pay, iCloud, or even the faster processor. The iPhone 6 is about a half-inch taller than the iPhone 5S and has smooth, rounded corners. It's a bit more "grab and go" than older iPhones, which helped make it more portable during my day. And battery life has hit a tipping point for me. I used to rely heavily on backup battery cases like the Mophie Juice Pack (and I still use them) but the iPhone 6 can last just about all day for normal use (email, browsing, and texting) without that case, so it's not quite as critically important that you carry a backup battery.

That said, there's a feature on the Samsung Galaxy S5 that is missing on the iPhone 6. You can use an "ultra" power saving mode on the Galaxy S5 that turns the screen black and white, enables only the most basic apps for texting and calls, and makes the device last for a day or two longer. It's helpful for business users who really need to stay in touch.

It's also worth pointing out that the Nokia Lumia 635 does a better job with voice commands than Siri on an iPhone 6. The assistant, known as Cortana, can warn you about heavy traffic on the way to a meeting location automatically, only allow phone calls and texts from an "inner circle" if you have told her not to let anyone bother you, and let you know about any weather issues in a destination city as you fly by (the phone automatically reads your flight plans). The Nokia 635 also offers all of the Microsoft mobile apps like Outlook and Word, which may integrate into your business ops more easily.

There's a lot of competition from other phonemakers as well--the HTC One M8 feels more durable--as though it would survive a fall or jostling in your luggage--than the iPhone 6. The Samsung Galaxy Alpha is also a highly durable phone. That said, there are still apps that debut on the iPhone 6 before they make their way over to Android. That's important for anyone in business because there could be an app--say, something for renting a car on a trip or texting in groups--that helps you get an edge.

It's not as much of a differentiator anymore, however. Overall the iPhone 6 is an improvement over previous models because of its bigger screen, longer all-day battery life, the new Apple Pay system for retail purchases, and a more portable, rounded design. It's still a clear smartphone leader; the competition is biting a little harder on its heels.