Getting a complete understanding of the pros and and cons of various hardware is very difficult.
So on what basis do you make a choice?
Here is a collection of questions and some attempted answers. Please add and Enjoy!
CUDA: is the SLI bridge important ?
The Scalable Link Interface bridge has lower bandwidth than the PCI e bus. SLI makes the two cards look like a single device from the host. The memory size of this "virtual device" is the same as that of one of the cards. So, the memory available to CUDA programs becomes half of what it actually is. A CUDA program that runs against a SLI setup must copy all the work to the one virtual card, and then the cards must distribute the work over the SLI bridge. Ref:stackoverflow
Is the PCIe version important?
Are more GPU cores always better?
I would figure it would be problem dependent, but dont know?