I haven't seen this discussed anywhere so forgive me if this is redundant. I was comparing the SP4 to the SB, and I realized that the SP4 uses a 6th Gen 2.2-GHz Intel Core i7-6650U processor with Intel Iris graphics 54, while the SB uses a 6th Gen 2.6-GHz Intel Core i7-6600U processor with Intel HD graphics 520. What this means is that you are getting a "better" CPU with the i7 version of the SP4 vs. a SB i7 CPU. The graphics processor is better, I would venture to say, by far, than the one in the SB. That being said, it is widely known that you can get the dedicated graphics in the SB, that's unavailable in the SP4. The Iris 540 graphics is just slightly behind the performance of the dedicated nvidia graphics processor in the SB, however, when the keyboards are detached from both units, the SP4 uses a 540 Iris graphics processor, while the SB reverts to the 520 HD processor that is the exact same one that's in the i5 CPU. To make a long story short, if you are using the SP4 and the SB as tablets, you are better off with the SP4 as it has a more powerful processor and graphics processor than the more expensive SB. I believe that most graphics artists are using the tablet form of the units to do their drawing and sketches on, so the SP4 comes out ahead of the SB in graphics performance power. The screen is larger on the SB however, so there is that. I don't know why the designers at Microsoft did that, but it is currently the case.