If your budget can stretch to it, we'd advise opting for the £399 64GB WiFi-only model, which should be sufficient space for most users (whereas you're likely to run out of room on the 16GB model in no time).
£399 would get you a 16GB iPad Air 2, but we'd prefer to sacrifice screen estate and a little bit of power (which we'll talk about in this review) and have 64GB with an overall great 7.9in tablet than regret our decision to go for 16GB in the future.
The iPad mini 2 is still available, and there's a 32GB model starting at £259 that might be an option, but then you miss out on Touch ID, a better camera, a thinner design and a more powerful processor.
For those in the US, the iPad mini 4 starts at $399 and ranges up to $599 for the 128GB model.
iPad mini 4 review: Design and build
The iPad mini 4 is essentially a smaller version of the iPad Air 2, both inside and out. It's certainly a much bigger update than the update between the iPad mini 2 and iPad mini 3 was (Apple simply added the Touch ID fingerprint sensor and a gold colour option but left the design and specs the same), with a new, thinner design and loads of internal improvements.
First, let's take a look at design and build. It's a really, really good-looking tablet, still available in Gold, Silver and Space Grey but with a thinner chassis and some new Smart Cover colour options that look fantastic (and you'll need to get a new Smart Cover even if you've already got one for your older iPad mini, because the magnets seem to have been repositioned). Pair that with one of Apple's new Silicone Cases for the iPad mini 4 for all-round protection.
We've gone for a Gold model with a Midnight Blue Smart Cover and we think it looks gorgeous, with its premium aluminium finish and smooth rounded edges, plus its now super-slim 6.1mm. That's 18% thinner than its already thin predecessor.
It is also lighter, at just 299g (or 304g if you opt for the cellular model), so you'll be able to pop this iPad into a small bag or even a large pocket and you'll hardly notice it's there.
So all together, those measurements are 203.2 x 134.8 x 6.1mm, at 299g. That's compared with the iPad Air 2's 240 x 169.5 x 6.1mm at 437g, so it's certainly more portable than it's bigger sibling, though of course you'll get less screen estate at 7.9in diagonally compared with the Air 2's 9.7in.
Aside from that, there's nothing particularly noticeably different in terms of design between the iPad mini 4 and its predecessors. It has lost its mute/lock rotation slider, just like the iPad Air 2 did, but you can quickly and easily access those settings within the Control Centre panel by swiping up from the bottom of the screen.
iPad mini 4 review: Hardware and performance
Taking a closer look at that 7.9in display on the iPad mini 4, you'll find that it's the same resolution as the iPad mini 3 and 2, as well as the iPad Air 2 and iPad Air, at 2048 x 1536 pixels. That equates to a 326 pixels per inch pixel density, higher than the Air and Air 2's 264 ppi.
That's not to say that the iPad mini 4 hasn't had some screen improvements, though. The resolution may be the same, but there's a new anti-reflective coating to help with use outside in the sun, and better still Apple has removed the gap between the cover glass and LCD (all part of the slimming process) to make the tablet feel more solid and dramatically improve the contrast.
The result is a crisp, clear screen that offers stunning colours that is ideal for watching videos or playing games. Of course, the bigger screen on the iPad Air 2 is even better for videos, and while both tablets support the new Split Screen feature in iOS 9, there's no doubt that running two apps side-by-side is a better experience on the bigger screen, but it's a sacrifice many will be happy to make in exchange for more portability and a bit of a saving when it comes to cash.
Inside the iPad mini 4 is a new A8 chip compared with the A7 from the iPad mini 3 and iPad mini 2, which represents a big speed boost (although it's not quite as fast as the A8X you'll find in the iPad Air 2). That's paired with an M8 co-processor that takes on all of the sensors to ease pressure on the A8, helping to keep things running more efficiently.
Our Geekbench 3 processor test found that the iPad mini 4 managed 1719 in the single-core test and 3101 in the multi-core test. That's compared with the Air 2's 1816 and 4523 respectively, which reveals that apps requiring more than one processor core should be much faster in the Air, but any that only need a single core should run at almost the same speed.
It's impressive stuff for an iPad of its size, and in reality you'll find that the iPad mini 4 is a smooth, speedy machine, even when running two apps at once with Apple's new multitasking tools.
Graphics power is good, too, although still not as good as the Air 2. The mini 4 managed 37fps and 15fps in the T-Rex and Manhattan GFXBench tests respectively, compared with the 52fps and 25fps achieved by the Air 2.
But it is much faster than the iPad mini 2 and iPad mini 3, which scored 22fps in T-Rex and 9fps in Manhattan.
You'll still find the Touch ID fingerprint sensor beneath the Home button with the iPad mini 4, but it hasn't been upgraded to the new, super-fast generation boasted by the iPhone 6s and 6s Plus. Still, it's a great feature for added security and convenience, plus Apple Pay.
The iPad mini 4, as mentioned, is available in 16GB, 64GB and 128GB models, and each of those offers the option of WiFi-only or WiFi + Cellular if you want mobile connectivity.
That WiFi is 802.11ac, which can theoretically run up to 866Mbps, and there's Bluetooth 4.2.
When it comes to battery life, the iPad mini 4 achieved a score of 3975 in the GeekBench 3 battery test. You can expect the tablet to last for around 6 hours of active use but if you only use it from time to time that battery life can stretch to days if not weeks.
The battery benchmark score for the iPad mini 4 is actually lower than the iPad mini 3's score of 4098 and lower than the iPad mini 2's 3990, and in fact comes in as the iPad with the worst battery life out of all of Apple's range, but not my a large margin.
iPad mini 4 review: Cameras
We're becoming slightly more accustomed to the idea of taking photos on a tablet, particularly when it's an iPad mini, so we know that many people will be pleased to hear that the rear camera has been bumped up from 5Mp to 8Mp, which isn't bad at all. It has quick auto-focus and good face detection, too.
The photos below have been resized to 1600x1200 pixels, down from 3264x2448 (click to enlarge)
You'll also get Burst mode and Slo-Mo video (120fps at 720p) thanks to the A8 chip. Panoramas can be captured at up to 43Mp and look fantastic.
Video is 1080p at 30fps, and is great quality with accurate colours and sharp details, up until you start trying to shoot in low light, and the same goes for still photos, but for a tablet you're looking at a good camera that'll outshine many rivals.
On the front, you'll find a 1.2Mp camera, which is not so great, but it is still the same as the one found in the iPad Air 2.