To be fair, given the challenges of cramming a laptop into a tablet form factor, there need to be some compromises. Unfortunately, I think that MS compromised too much to chase the iPad. The only time anyone will notice the few mm difference is in review photos comparing the thickness to that of an iPad. The SP2 has much better cooling resulting in less throttling and better sustained performance. If the SP2 form factor is not a deal breaker for you, it may be the better choice. As far as the i7 goes, I think that it borders on fraud since it offers virtually no practical advantage over the i5.So now I'm wondering: just why are we being sold i5's and i7's that can't sustain their speed? What is the good of having this CPU speed if it can only be maintained for short bursts?? Honestly, this is getting close to "false advertising" for me... and I love the SP3 overall so don't be fast to dismiss me as a hater
You may also want to explore external cooling solutions.