With the Series 4's arrival having ushered in a price cut to the Series 3, it's not necessarily straightforward which of them you should choose. What new stuff does the Apple watch series 4 bring?
Apple Watches have long been offered in 38mm and 42mm sizes. However, apparently in a bid to enlarge the screens and so extend the functionality, Apple has bumped up the sizes to 40mm and 44mm for the Series 4. Not that this has impacted hugely on the overall form factor...
With the new display - and we'll look more at that a little later - more edge-to-edge than that of the Series 3, even the new 40mm Watch offers a larger viewable display area than the old 42mm model. Furthermore, the casings have actually been slashed in depth - from 11.4mm to 10.7mm.
Like every earlier model of the Apple Watch, the Series 4 comes with an OLED display. However, whereas the Retina displays of the Series 3 measured - respectively - 272x340 pixels for the 38mm model and 312x390 pixels on the 42mm version, the screen real estate is now over 30% bigger.
That applies to both the 40mm and 44mm versions of the Apple Watch Series 4, as the former measures 324x394 pixels - a 35% increase - while the latter spans 368x448 pixels, 32% larger.
What do these increases really mean in practice? Basically, that there is now more that can be fitted onto the screen - and this has great implications for the increased functionality of the Series 4.
While the mantra that "Apple doesn't innovate anymore" appears to have set in among many press circles, it's not a belief that should be held about Apple's treatment of the Watch. Every yearly reiteration has brought meaningful new features, and the Series 4 is certainly no exception.
Perhaps the headline new inclusion this time around has to be that of the in-built ECG support. ECG stands for electrocardiography - and, while the Series 3 still features an optical heart sensor, the Series 4 has gone further in becoming the first ECG product of over-the-counter availability.
The FDA-approved ECG support in the Series 4 makes the device capable of measuring your heartbeat's electrical activity. As a result, numerous heart conditions could be diagnosed.
Apple has given the Series 4 the company's new S4 chip. This 64-bit dual-core processor, Apple has claimed, can deliver double the performance of the Apple Watch Series 3. The Series 4 enclosure also houses Apple's refreshed W3 wireless chip. The Series 3 uses an S3 chip and W2 wireless chip.
The Series 4 also includes an improved accelerometer of up to 32 g-forces; that's twice the number of the Series 3 accelerometer. Due to how the Series 4 accelerometer is set up with the device's gyroscope, that device can handle more complex tasks - among them the new fall detection feature.
Especially comforting for elderly users, this feature will kick in if the Series 4, through analyzing wrist trajectory and impact acceleration, detects that the wearer has taken a hard fall. The device can then help the user to easily call emergency services, should this be deemed necessary.
The most notable new feature of the Series 3 was arguably its onboard cellular connectivity; no longer did Watch users need to keep their Watches tethered to an iPhone for this connectivity.
That feature remains present with the Series 4. You can identify the LTE models from the red ring on the digital crown. That makes a much nicer and subtler change from the distractingly prominent red dot adorning LTE versions of the Series 3.