Only you can decide. For me, it is the SP2. I was hoping msoft would keep the SP2 as well as the SP3 due to the smaller form factor as it is much more convenient for me, as a tablet in the 10.6" size compared to the 12".
Under general use the throttling mentioned is of little importance unless you type at 30,000 word per minute.
The screen resolution is also of small importance as the greatest cost of higher resolution is battery drain but the SP3 has that covered anyway.
The weight difference is also doodly squat, it is measured in ounces. Hell, my Miix-8" is half th weight of the SP3 and I still find that heavy to hold for reading, so weight, within limits, is also not really an issue.
I waited to buy the SP2 as I was hoping msoft would bring out a revised lighter version along side the SP3, but when it was clear that the SP2 was dead, I bought a new-old-stock i5-SP2. It (they, actually bought two) cost me around the same as an SP3 and it still had some msoft warranty, so I guess that would answer your question from MY perspective.