The iPhone 6 and its more sizable sibling, the iPhone 6 Plus, are now available for order if you live in one of the 10 initial launch countries. But when are the newest handsets coming to an Apple Store near you and how do you decide which of the two devices is right for you?

The latest iPhones will officially go on sale on September 19 in the US, Canada, Puerto Rico, Japan, Singapore, Hong Kong, Australia, the UK, France and Germany and reservations can be made from September 12, either via Apple's website or with network carriers and retailers.

The 6 or the 6 Plus?

Both handsets boast almost identical specifications -- the same processor, a fingerprint scanner integrated into the home key, a thinner, lightweight design and, for those living in the US, integrated mobile payments.

The only real difference between the two is screen size. The iPhone 6 has a 4.7-inch screen but at 5.5-inches the display on the iPhone 6 Plus makes it a phablet.

And that means that it's going to be a bit tricky to use with a single hand or to slip into a pocket.

To help consumers understand this jump in size, a number of tech sites, including Arstechnica have made templates that you can download, print and cut out to get some idea of how big this phone really is.

But as well as being bulkier than iPhones of the past, the Plus is going to be great for watching video, gaming and for a bit of productivity too.

Apple has tweaked the handset's operating system so that the phone works equally well when held in landscape and portrait modes, making it easy to switch between apps or view two apps side-by-side, and has added extra commands to the homekey so that single-handed use is still possible for some things like checking notifications.

The other differences between the two handsets are image stabilization and battery life.

Both phones have the same camera, but the Plus has the mechanics and software to eliminate camera shake too -- but it is a bigger device and therefore harder to hold still.

The phablet's battery is also bigger and Apple claims that means it will last for 12 hours when web browsing (10 hours or the iPhone 6).

When are they coming?

After the initial roll-out on September 19, consumers in Switzerland, Italy, New Zealand, Sweden, Netherlands, Spain, Denmark, Ireland, Norway, Luxembourg, Russia, Austria, Turkey, Finland, Taiwan, Belgium and Portugal will be able to reserve an iPhone from September 26.

Apple says that before the end of 2014 the devices will be on sale in 115 countries around the world.