there's no way you should get an i3 64GB over the i5 128 GB. if you plan on doing a lot with a computer, you can't go with only 64GB and with a far inferior CPU.
Plus, the SP3 has more pixels to drive which means with the same CPU, it's slower. So an SP2 with i5 is faster than an SP3 with i5. So now if you're giving the SP3 the i3, that just makes it worse.
the only reason to go with the SP3 in this case is if you really want the larger screen. but if you can handle the SP2 screen size, it's would be much more beneficial to go with that. You want room to grow with a machine. I already think 128 GB is barely doable because remember Windows apps only install on drive C:. And even if you install something like Adobe Creative Suite on your memory card on drive D:, some parts of the program still gets installed in various places on drive C:.
As for connected standby, I wish the SP2 had it. It's wonderful on my Surface RT. I just plop down the keyboard and it wakes up instantly.