You already have the answer to your question.
As far as I see it, the dGPU will be only beneficial for demanding games, heavy 3D work...
If you're planning on using Solidworks, Maya, Lightwave, or any 3d creation or CAD application get the Iris pro one. It is significantly faster for those tasks and not that far behind the GT650M-750M for gaming
The iGPU, will reduces the complexity of your system. Eliminates the graphics mode switching. Less power consumption, prolongs the battery life.
On the math side:
$2300 vs $2650 is 8.6% or $350.
What can you do with $350?
Buy some software (Games) you always wanted.
Buy USB stick, or External Drive for back ups.
Keep it for rainy days :)
On the other side:
The $350 is not for the GeForce GT650M alone. Check the system specs in more details to find the differences you care about.
My vote would be for the iGPU since it comes with newer model that brings other engineering improvements with it.
One trick is to drag their preferences files out onto the desktop and restart the apps - they will build new ones, though you'll have to enter your settings again.
You might check if these are taking App Naps - look in Activity Monitor.
Best Answer
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.
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:
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.