HTC and Sony have everything to fight for in the flagship smartphone race. With Samsung typically walking away with huge sales, it's down to the HTC One (M8) and the Sony Xperia Z2 to prove they have what it takes.

But these devices aren't just also-rans, they are both technological marvels, packed full of features and functionality, looking to give you the best smartphone experience through this year and into the next.

But which device, between the HTC One (M8) to the Sony Xperia Z2 is the best? We've lived with, and reviewed, both, so this isn't just a battle of specs, this is a bone fide fight for supremacy.

The HTC One (M8) has a smaller, sharper, display

The HTC One (M8) comes with a 5-inch display, fractionally smaller than the 5.2-inch on the Sony Xperia Z2. Both devices have the same 1920 x 1080 pixel resolution, but the difference in size means a slightly lower pixel density on the Xperia Z2 at 423ppi to HTC's 441ppi.

That minor difference you won't really notice as both displays are magnificent. The Sony is perhaps the most vibrant of the two, but Sony's display tech can lead to slightly unrealistic colours: the X-Reality setting makes colours a little too punchy.

In reality there's little to choose between the two, but the Sony has one downside: if you're wearing polarising sunglasses you might not be able to see the display when it's in landscape, i.e., when using the camera. It's not a huge point, but irritating for taking holiday snaps.

READ: HTC One (M8) review

HTC wins with better design

The HTC One (M8) measures 146.36 x 70.6 x 9.35mm and weighs 160g, the Sony Xperia Z2 measures 146.8 x 73.3 x 8.2mm and hits the scales at 163g. But these numbers only tell a tiny part of the design story. Both the HTC One (M8) and the Sony Xperia Z2 offer a solid, premium build, but the design is very different.

The HTC One (M8) comes with a curvaceous aluminium body and front-facing BoomSound speakers. It feels great to hold, the curves really nestling into your hand. It looks sumptuous and won't fail to turn heads, but also offers that practicality by being lovely to use.

The Sony Xperia Z2 is also a great looking device and comes with a tempered glass finish with an aluminium trim for a flat monolithic effect. Although you get IP55 dust-resistance as well as IP58 waterproof certification on the Z2, the extra bezel top and bottom feels like wasted space. The flat design also makes the Xperia Z2 more uncomfortable to hold and less practical in daily use.

So although those stats are pretty close, with the Z2 packing in a larger display, the HTC One (M8) is a much nicer device to actually use. 

Sony Xperia Z2 offers more megapixels on rear camera but not front

The HTC One (M8) has a Duo Camera on the rear, with a UltraPixel sensor that captures an image and a secondary lens to capture depth information. It is a clever arrangement, but the HTC One camera lacks resolution, even if it is very fast to focus and capture.

The Sony Xperia Z2 on the other hand has a 20.7-megapixel snapper on the rear, with a range of clever features including 4K video, something the M8 can't offer. The Xperia Z2 rarely uses all that resolution, but even at the default 8-megapixels, returns some very nice results in most conditions, with plenty of flexibility.

READ: Sony Xpera Z2 review

When it comes to the front camera, the HTC One (M8) has a 5-megapixel snapper and the Sony Xperia Z2 offers a 2.2-megapixel front-facing camera. If you want the best selfie, then the HTC One is the phone for you, returning great results.

If you're after better photos from the rear camera, although the HTC One (M8) enables some great effects with the Duo Camera arrangement, the Xperia Z2 in straight shooting will most likely give you better results.

Same processor, but bigger battery and more RAM on Xperia Z2

Both the HTC One (M8) and the Sony Xperia Z2 come with the latest 2.3GHz quad-core Qualcomm Snapdragon 801 chipset, but you will find 2GB of RAM on the HTC and 3GB on the Sony.

The result is that in a head-to-head, the Xperia Z2 is often slightly faster to open large apps. However, that's not the end of the story because the HTC One (M8) feels incredibly slick and fast moving around the UI, so that slight Sony advantage doesn't really manifest itself in real world use. Both devices have loads of power and are very fast, so it's a closely comparable experience.

In terms of the battery, the HTC One (M8) comes with a 2,600mAh battery, the Sony Xperia Z2 has a 3,200mAh battery. Both devices will get you through the day fairly easily, but the Sony has the capacity advantage.

HTC has an extreme power saver mode, while the Sony offers great granular control over apps using the Stamina Mode.

More storage on the HTC One (M8)

As you would expect, the HTC One (M8) and the Sony Xperia Z2 come with the usuals when it comes to connectivity. You will find 4G LTE, Wi-Fi, NFC and Bluetooth on both devices.

When it comes to storage, the HTC One (M8) offers 16GB internal storage just like the Xperia Z2 and both come with microSD support for further storage expansion. The HTC One (M8) can support up to 128GB via its microSD slot while the Sony Xperia Z2 can only handle up to 64GB.

The HTC One (M8) also comes with an additional 50GB of Google Drive space.

Audio face-off

Both the HTC One (M8) and the Sony Xperia Z2 offer front-facing speakers. For the HTC One, that's the tried and tested BoomSound speakers, but they are louder than ever before on the M8. The performance is class-leading, easily better than those on the Xperia Z2. If you like ditching the headphones, the HTC One (M8) is the device for you.

However, Sony has an audio trick of its own. It has on-board noise cancellation, so when you connect the Sony MDR-NC31EM headphones, you'll get great noise cancellation without needing bulky headphones. In the UK those headphones will come in the box, which is a really good extra.

Headphones or speakers? Both devices offer something special.

Both devices run on Android 4.4, with customisation

The HTC One (M8) and the Sony Xperia Z2 both come with Google's latest software - Android 4.4 KitKat.

Sony has added the usual customisation to the Xperia Z2, adding plenty of Sony features in the process. There's a big push on Sony's movies, music and gaming content, with the addition of the What's New portal in the Google Now shortcut. There's a fair amount of bloat too, with lots of Sony apps added. 

Sony's software doesn't seem to have moved forward much over previous devices, but there's no shortage of functionality.

The HTC One (M8) offers Sense 6.0, which is visually refined over previous HTC devices and looks and feels more mature than Sony's offering, although this comes down to personal preference. HTC also offers plenty of lovely features through it's highlight videos and we're impressed at just how slick and fast the Sense 6.0 UI is.

We'd side with HTC on this one, but personal taste plays a big part.

Conclusion

These two devices really are neck and neck on the spec sheet, being very closely matched. There are pros and cons on both sides. The Sony Xperia Z2 offers a better overall camera experience, but the HTC camera is often faster and offers some unique features with plenty of appeal.

The Xperia Z2 has a larger display, although can get a little unrealistic on the colours, but both screens are very nice to use.

The HTC offers are more practical design: it's nicer to hold and nicer to use day-to-day. Although the measurements are similar, the HTC feels smaller and fits into your hand better. 

The M8 also offers better sound quality from those BoomSound speakers, has a slicker user interface and feels faster in daily use.

Both devices offer performance and power, but are also good when it comes to the battery life, with stamina to carry that performance through the day. We'd pick the HTC One, however, because once you've lived with both, the design really does make a difference.

READ: HTC One (M8) vs Samsung Galaxy S5: What's the difference?