Sony's previous flagship, the Xperia Z has had a surprisingly short spell as top dog because now we have the Xperia Z1 which addresses all the Z's failings. What makes the Z1 as good as it gets in Sony's (or anyone else's for that matter) smartphone universe is a more powerful quad-core processor, much improved 1080p screen, 20-megapixel camera and a waterproof glass and aluminium body that doesn't require you to faff about with a plug in the 3.5mm audio jack. Could this be the best smartphone in the world?
The Z1 is fairly slim at just under 9mm but the glass and aluminium it's made off makes it quite a heavy beast. It weighs 170g which is 25g more than the hardly featherweight Xperia Z so you know you've got something in your pocket. Still, the upside is that this is quite clearly a very high quality piece of kit as soon as you pick it up. It feels very solid and expensive, much like a large iPhone 5 would feel.
Like the Z and Z Ultra the 1 is waterproof (an area that Sony seems keen to make its own) so the SIM card, microUSB and microSD card slots - the Z1 will take cards up to 64GB in capacity - are all protected behind covers so that it can stay underwater to a depth of up to 1.5 meters for up to half an hour. Handily unlike the Z there's no cover for the 3.5mm headphone jack so you can keep water and grit out without having to reseal the port every time you unplug your headphones.
The five-inch screen has the same 1920 x 1080 resolution as its predecessor with a pixel density of 441ppi and to be honest, it's hard to imagine how it could be much better. It is terrifically sharp and colours look very natural thanks to Sony's Triluminos technology derived from its latest high-end TVs.
Exactly how this image processing voodoo works is a bit of grey area but work it does so whether you're watching HD movies or looking at dense web pages or still images it's a truly terrific screen.
The original Xperia Z had a quad core processor, but it's now been bumped up from 1.5GHz to 2.2GHz and backed by a full 2GB RAM making it one of the highest spec smartphone smartphones money can buy. And sure enough, in the AnTuTu benchmark test it delivered a score of nearly 35,000 which is 10,000-odd points better than the Samsung Galaxy S4 cam manage.
The improved screen aside the big news here is that the camera has gone from 13 megapixels to 20.7 megapixels which is a massively higher spec than you'll find on any smartphone with the exception of Nokia's monster Lumia 1020. There's a dedicated shutter button on the side too which wasn't present on the Z. It's certainly a fine, fine camera, with Sony's 1/2.3" Exmor RS sensor and F/2.0 G Lens to help improve low light pics, and a range of settings to play with including Smile Shutter, Face Registration and Burst.
Thankfully Sony has given the Z1 a large 3,000mAh battery because it's a very powerful phone, and that takes its toll. You will get a full day of heavy use out of a charge but not an awful lot more.
The final area where the Z1 trumps it's predecessors is with it's loudspeaker. This is an area Sony has traditionally been a but weak in but the Z1's speaker, despite being water tight, it pretty good. Not HTC One-good, but certainly a big step forward from the Xperia Z. Like all Xperias but unlike most Samsung Galaxys the battery is fixed in place. That is a good or bad thing depending only your personal preference.
If the body, screen and camera weren't enough to tempt you from a Galaxy S4 there's also the final issue that Sony's take on Android 4.2.2 is less overburdened with toys and frankly rather pointless features that Samsung's. The Z1 is just an easier bit of kit to get with grips with. Add to that Sony's media apps which are simply superb and the Z1 makes for the more satisfying user experience.
Verdict: The Sony Xperia Z1 makes some key improvements to the Z which was already a pretty good smartphone. The screen is superb, the processor is the most powerful I've seen in a smartphone rather than a a phablet and the camera is exceptional. It's not cheap I grant you but it's waterproof, looks great, is built like a brick outhouse and is extremely powerful. The best smartphone in the world? Yes.
Info: Sony's Xperia Z1 page.