What is the difference between Apple Watch 1 2 &3?

Hi

Apple no longer sells new Apple Watch Series 2 models. It instead sells the newer Series 3 model range.

Whilst you may find new Series 2 models still available from some Apple Authorised Resellers, you may prefer to instead consider buying a Series 3 model. Differences between Series 2 and Series 3 models include that Series 3 models have a faster processor and a more power-efficient Bluetooth / Wi-Fi chip.

Series 3 models include options for Series 3 (GPS), which does not have a built-in cellular capability and Series 3 (GPS + Cellular), which supports built-in cellular features, subject to having a compatible service plan from a supported carrier.

Differences between Series 1 and Series 3 models include that Series 3 models offer:

• A higher level of water resistance, including during general daily use.
• A faster processor.
• Siri speaks.
• A brighter display (twice as bright).
• A USB Power Adapter is included.
• Built-in GPS.
• A barometric altimeter (used to track flights climbed during general daily wear and, during outdoor workouts, elevation gain).

Technical specifications can be compared here:

• Apple Watch Series 1 - Technical Specifications
• Apple Watch Series 2 - Technical Specifications
• Apple Watch Series 3 - Technical Specifications

Differences between currently available models are detailed here:

• Apple Watch - Compare - Apple
• Apple Watch Series 1 - Apple
• Apple Watch Series 3 - Apple

More information:

Watch - Apple

You can go here to see a comparison of the Apple Watch Series 1 and Series 3. Apple no longer sells the Apple Watch Series 2. See if that information helps. Apple Watch - Compare - Apple

As far as which one is better, would be dependent on his usages.