Okay this is just a piss take topic, if you had unlimited money to spend on a single board PC, for anything you want, not just programming, and why?
Link the specs/name below
I would use the Jetson TK1, reason for this is due to its GPU, the GPU is the best I have seen on embedded, and I like raw power, and the Tegra K1 would give me this, The Mini PCI also allows for a nice expansion based on the task at hand, it would mostly be used for a ssd, but if I was away, I could easily flash the board with a wifi module and it gives me easy net access when needed, and I would be more comfortable with Linux and a TK1 on public wifi due to the improved system security within Linux.
Adding to that with the GPU power, I could easily use a 3D program to print a nice case for the system, while I have no experience with 3D printers, and I have no idea what specs work best with the programs for designing cases, I guess if this was my only PC, the TK1 would give me the best performance.
The downside to having a TK1 is I cant use batteries like with the RPi, or at least to my knowledge, if so I expect the processor would be rather efficient, but no where near the draw of the Rpi.
But as I would use this the PC as a desktop and a main one as that, the TK1 would suit my needs better than the XU3 due to the GPU.