Which model to buy is a matter of personal preference.
All Apple Watch bands are compatible with all Apple Watch models of the same case size (38mm / 42mm):
Buy Apple Watch Bands - Apple
Keep in mind that:
- Apple Watch Series 3 (GPS + Cellular) requires an iPhone 6 or newer with the latest version of iOS.
- Apple Watch Series 3 (GPS) and all other models require an iPhone 5s or newer with the latest version of iOS.
- Set up your Apple Watch - Apple Support
All models of Apple Watch can be used, for example, to make calls and to send and receive messages, subject to connectivity (see the further information below for more details):
Differences between Series 1 and Series 3 models include that Series 3 models offer:
- A faster processor.
- A higher level of water resistance.
- Siri speaks.
- A brighter display (twice as bright).
- Built-in GPS.
- A barometric altimeter (used to track flights climbed during general daily wear and, during outdoor workouts, elevation gain).
- A USB Power Adapter is included.
All models of Apple Watch include support for connecting to a compatible Wi-Fi network if a Bluetooth connection with the paired iPhone is not available (see the related below).
Apple Watch Series 3 (GPS + Cellular) models also include a built-in cellular feature. This requires a service plan for your iPhone that specifically includes support for the watch, including the carrier activating the watch on the plan. An activation fee and additional monthly fee may apply:
Apple Watch - Carriers - Apple
Other differences between Series 3 (GPS + Cellular) models and Series 3 (GPS) models include that (GPS + Cellular) models:
- Have double the storage capacity of GPS-only models.
- Have a ceramic back (instead of a composite back).
- Are compatible with Apple's recently announced AirPower wireless charging mat, which is due to be released next year:
- Include options for Stainless Steel and Space Black Stainless Steel cases (all GPS-only models are aluminium).
- Stainless Steel and Ceramic (Edition) case models have a sapphire crystal, which is more scratch resistant than Ion-X Glass.
The functions that are available on Apple Watch when it is away from your iPhone depend on various factors including:
Features and requirements that apply under various circumstances are detailed here, including within the footnotes:
How to use your Apple Watch without your iPhone nearby - Apple Support