Mobile app development using Xcode. Single Graphics vs Dual Graphics?
A Mac with dual graphics (integrated + dedicated) is preferred when working on graphic intensive projects.
Generally speaking, a more recently introduced model is equipped with better internals (such as newer generation of processor and faster RAM/internal storage).
You should pay attention to the machine specifications and your use-case to choose an appropriate one as it can differ from person to person and task to task. You need to base your decision on criterion such as:
Processor generation, frequency and performance gain (year-over-year)
Amount and frequency of RAM
Amount of speed of internal storage
Screen size/real estate and supported resolutions
Ports, their speed and support for external display and accessories.
Can any one please tell me which one is better for Xcode based on the year?
Depends on your specific use case (and budget) as discussed above. You can compare the detailed specs for the two mentioned models and base your decision on that. Check the following link:
Also what is the difference between single and dual graphics?
A MacBook with dual graphics quite literally means that it is equipped with dual graphics card. The one with single graphics card comes equipped with Intel Integrated graphics (which is generally speaking fine for day to day usage). Dual graphics MacBook Pro includes a dedicated graphics card in addition to the Intel Integrated card, and the operating system includes the support for automatic switching between the two.
A dual graphics machine is preferred when you need good performance in graphics intensive tasks/projects, gaming, or have a project that needs to utilize GPU compute.