Hello, can Udoo x86 ultra Pentium N3710 2.56 GHZ computer be for development with Visual Studio C++ for developing with C++/CX DirectX Windows games AAA, Unity3D, Leadwerks Engine, and other development with maybe C# games, can it replace expensive Intel NUC core i3 fanless from quietpc shop?
N3710 is Intel ATOM class processor. Most of the Intel NUCs are using desktop i3/i5/i7 CPUs. You have to decide what you need then make platform choices.
Intel classify the N3710 as Pentium class: https://ark.intel.com/products/91830/Intel-Pentium-Processor-N3710-2M-Cache-up-to-2_56-GHz For running a code editor, the board is a good choice, however, if your development environment involves heavy use of displaying/compiling 3D graphics, you may not have an ideal experience.
Here I am talking about the internal CPU architecture, capabilities (e.g., extended x86 instruction set, capabilities stripped, etc.) thus ATOM https://en.wikipedia.org/wiki/Intel_Atom and CORE architecture (such as recent Gen 6, 7, and 8) https://en.wikipedia.org/wiki/Intel_Core . Educated users familiar with this industry should know the rationale and technologies behind. On the other hand, Intel marketing had conveniently created a different criteria for general consumers such as Celeron, Pentium, Core i3, i5, i7, Xeon, etc. Most of the criteria is based on general usage on common tasks. AT the end of the day, it is the end user's own decision on what's important to his/her tasks and make the selection. Again, I am not saying any specific product's pro and con but trying to ask the OP to understand what are the differences on machine architecture and start there.