Samsung turned heads when it announced the Samsung Galaxy S6 earlier in 2015 and it was quickly heralded as one of the top Android phones of the year.
Sony stumbled with the Xperia Z3+, an intermediary measure, but has now revealed its true flagship for 2015, the Sony Xperia Z5.
So what's the difference between those pocketable powerhouses? Which handset is going to give you more in the showdown between these old rivals? We have put them up against each other to give you a quick rundown of the headline differences.
Samsung Galaxy S6 is smaller and thinner, but not waterproof
Although offering uniquely different designs, there's a great deal of similarity between Sony and Samsung when it comes to build. Both handsets feature a metal frame sandwiched between glass front and rear.
But that's where the similarities end. Samsung has a curvier and slimmer device, measuring 143.4 x 70.5 x 6.8mm and weighing 138g, while the Xperia Z5 is 146 x 72 x 7.3mm and 154g, so bigger and heavier, although it also has a larger display.
Both handsets have a premium build and both feel great in the hand. Sony's phone is squarer, which might mean that Samsung's device is a little more comfortable to use for smaller hands. However, the Sony phone is waterproof.
The Samsung Galaxy S6 has a sharper display
The Sony Xperia Z5 has a 5.2-inch 1920 x 1080 pixel IPS LCD display, offering 428ppi. The Samsung Galaxy S6 has a 5.1-inch Super AMOLED display with a 2560 x 1440 pixel resolution for a pixel density of 576ppi.
Technically, the SGS6 display is better placed for producing finer detail. It packs in more pixels than Sony and the results are fantastic: the SGS6 display is excellent. The use of AMOLED means vibrancy to colours and lovely deep blacks.
However, the Xperia Z5 display is also excellent. It might be a lower resolution, but it's very capable with colours and offers excellent visuals. Samsung might just edge this one, but it's a closely fought battle.
Similar hardware, but Xperia Z5 has more storage
The Sony Xperia Z5 has a 64-bit octo-core Qualcomm Snapdragon 810 chipset with 3GB of RAM. The Samsung Galaxy S6 has a 64-bit octo-core Exynos chipset with 3GB of RAM.
That suggests that these devices are closely matched in performance and they are, but Snapdragon 810 has been plagued with a reputation for overheating - especially in the Xperia Z3+ released earlier in the year. The Samsung Exynos, however, has been a great performer.
The Xperia Z5 will come with 32GB of storage and supports microSD expansion up to 200GB. The SGS6 also starts with 32GB storage (64 and 128GB also available), but doesn't support microSD. Storage fans only have one choice here.
Both devices offer a fingerprint scanner. Sony places it over the standby button on the side, while Samsung's it built into the home button. Both will offer security and support for fingerprint authentication, although Smasung's scanner also doubles as a magnetic strip reader.
Sony Xperia Z5 has more rear camera megapixels
The Sony Xperia Z5 comes with an all new camera with a 23-megapixel sensor, and a whole range of advanced Sony technologies offering excellent image stabilisation. The Samsung Galaxy S6 has a fabulous 16-megapixel camera and has been one of the strongest performers of the year. Both have a 5-megapixel front-facing snapper.
Sony is promising the fastest autofocusing of any smartphone yet, but it's too early to judge the outright performance. The difference in resolution isn't going to win this battle, as Samsung has proved that it's very capable with the hardware it has.
The SGS6 offers a really handy camera quick launch shortcut with a double tap on the home button, but Sony will also quick launch using its dedicated camera button.
Sony Xperia Z5 will last longer
Sony knows what it is doing with batteries. There's a large 2900mAh battery offering fast charging, but no wireless charging. Sony says you'll get two days from it, and experience suggests that might be possible.
The Samsung Galaxy S6's biggest weakness is battery life. It has a smaller 2550mAh battery that struggles to last the day. But it does offer wireless charging and it's very fast to charge.
We think Sony will win the battery battle fairly easily.
Samsung stole the show with the launch of the SGS6 in March, but the Sony Xperia Z5 is a strong competitor. Samsung's design is a little more original, as Sony is only a small step away from its previous device, but the build of both is excellent. Samsung is lighter and more compact, but it isn't waterproof like the Sony.
The Samsung Galaxy S6 has an excellent display with a higher resolution and with the Exynos chipset, plenty of power, so it is likely to be slightly faster than the Sony handset.
However, Sony offers expandable storage and will almost certainly have much better endurance, with a larger battery.
Sony's camera remains a relative unknown so it's difficult to definitively say which might be better. Sony is talking the talk, but Samsung's camera is already walking the walk.
Of the two handsets, the Samsung is likely to be the one that wows the most, but the Sony Xperia Z5 is likely to be seen as the more practical phone.