Sony has quietly announced a new flagship, the Xperia Z3+ smartphone, which is identical to the Xperia Z4 handset that launched in Japan in April. The device was rumoured for several months, first as the Z4 and then more recently as the Z3+ so the launch won't come as too much of a surprise to those who have been following the speculation.

Like the Xperia Z4 did, the Xperia Z3+ makes some slight improvements on the Xperia Z3 flagship but the majority of the design and many of the elements remain the same as the predecessor.

To make it easy to see the differences, we have crunched the specs of the Xperia Z3+ and the Xperia Z3. Here is what you can expect to see from the worldwide version of Sony's newest flagship.

The Sony Xperia Z3+ brings with it the same OmniBalance design we have come to expect from the Xperia Z range, but Sony has refined it yet again with the new handset.

You'll still find the side power button, aluminium frame, tempered glass rear and rounded corners, but Sony has opened up the Micro USB port and removed the cover. This is the same as what it did for the Xperia M4 mid-range device that it launched at MWC in early March. The Xperia Z3+ will still be waterproof like the Xperia Z3 but it will be more convenient to charge.

In terms of footprint, the Xperia Z3+ measures 146 x 72 x 6.9mm, while the Xperia Z3 measures 146 x 72 x 7.3mm so the new device sheds a few pounds off its waistline and it also drops in weight from 152g to 144g.

The Xperia Z3+ has a 5.2-inch display that sports a resolution of 1920 x 1080 to offer a pixel density of 424ppi. This is the same as the Xperia Z3 so you shouldn't notice any difference in the two devices when it comes to the screen.

Despite many rumours claiming the Xperia Z3+ would step up to a Quad HD resolution like many of its competitors, this hasn't turned out to be the case. Sony has stuck to its Full HD resolution guns for the last couple of Xperia Z smartphones now, claiming battery life is more important, but some may be disappointed to hear the Xperia Z3+ doesn't offer a jump up to match the likes of the Galaxy S6.

Sony's Triluminos, X-Reality and Live Colour LED techologies were all on board the Xperia Z3 so expect these to also be present in the Xperia Z3+.

Sony has consistently marketed its Xperia Z range with the camera at the forefront and so it will come as no surprise that the Xperia Z3+ offers the 20.7-megaixel rear snapper of the Xperia Z3.

The same maximum ISO 12,800 sensitivity also appears on the Xperia Z3+ that was found with the Xperia Z3, as well as auto focus functionality. Like it's predecessor, the Xperia Z3+ is capable of 4K video capture and output, offers a 25mm wide-angle G Lens and 8x digital zoom.

The front-facing camera of the Xperia Z3+ does take it up a notch from the Xperia Z3 however, coming in at 5-megapixels compared to 2.2-megapixels. Sony has also added SteadyShot with Intelligent Active Mode and Superior Auto to the latest model. 

Under the hood, the Xperia Z3+ features a 64-bit octa-core Qualcomm Snapdragon 810 processor, which is a step up from the Qualcomm 801 processor found in the Xperia Z3.

Both offer 3GB of RAM but the Xperia Z3+ doubles the initial internal storage compared to the Xperia Z3. The Xperia Z3 comes with 16GB flash memory, while the Xperia Z3+ is listed as 32GB. Both are expandable via microSD up to 128GB.

So far, it doesn't seem like much has changed with the new handset, but interestingly, the Xperia Z3+ offers a smaller battery capacity than the Xperia Z3. The Xperia Z3+ will come with a 2900mAh battery compared to the 3100mAh capacity found in the Xperia Z3 but Sony has said that won't compromise on the two-day battery life.

As you would expect, the Xperia Z3+ will come with Android 5.0 Lollipop straight from the box and as the Xperia Z3 has now been updated to the latest software, you shouldn't see any difference in terms of user experience here.

Sony's skin will still be over the top, offering easy access to the Walkman, Entertainment, PS4 Remote Play and Xperia Lounge. The company has also added a couple of new audio technologies to the Xperia Z3+ including LDAC, which offers the ability to enjoy top quality music wirelessly, and automatic headset compensation (AHC) for personalised sound.

The Xperia Z3+ makes small improvements in numerous places over its predecessor, but it doesn't do anything drastic like Samsung did with the S6.

You get the same design but a little lighter and slimmer, and you get the same 5.2-inch Full HD display so you won't notice a great deal of difference to begin with, except for the open Micro-USB port.

Go a little deeper and under the bonnet however, and the Xperia Z3+ increases its power and internal storage, as well as improving its front-facing snapper. It does drop the battery capacity down however, and there will hardly any variation in software between the two devices, expect the audio technology and front camera additions.

In a nutshell, the Xperia Z3+ makes improvements over the Xperia Z3 as you would expect from a succeeding device, but the difference between the two is pretty minor. The Xperia Z3+ would win the numbers game but Sony has refined its already decent flagship, rather than given it an overhaul. Think of it a little like what Apple does every other year when it adds an "S" rather than give its new smartphone a new number.