We'll I'll give you a few answers.
First it really depends on what you use the machine for. The multicore is better, but that isn't going to make any difference to you if the software you run doesn't take advantage of it. Which depends on how it's written. If you're not using software written to take advantage of the multiple cores, you won't see much difference.
The other thing I'll say, is if you keep your machines a while, it's probably to your advantage to go all in and get the best one. Also I would second this if it's a primary machine. If it's secondary, and you want to save a few bucks, then maybe 1.2 is a better choice. But if it comes down to money for this machine, I would pick the larger HDD over the clock speed, because the larger hdd tend to read/write faster. Probably more noticeable improvement in that case.
For me personally, I'm highly interested in this score, and have been waiting for it before ordering because, I do graphics/video/photography work. Now I would never recommend this machine for graphics work, for me it will be secondary (I have a retina MBP for this), but on the off chance I ever have to do something minor on it (which happens in my line of work), I want to know it can handle it. I also deal with large file sizes. So in my case every little bit helps. If the 1.2 and 1.3 were largely on par with one another, I would save the time and the money and get the 1.2. However given some of the scores on Geekbench for the 1.2 I'm inclined to believe they are not. There are some pretty high scores on there for that one and what's posted here for that 1.3 doesn't seem right, which is why i'd like to see some more scores from other people.
