well for me when switching from my RT to the S2 I COULD feel a difference, also my wife too, so I don't think it's a psychology thing at all, that being said take it as you like but don't let that be just the deciding factor many many benefits to the S2 as compared to the RT which many times it has been posted
You didn't disprove it's psychological. It's the "practical" difference that matters. If you hold it in your hands for hours on end, then an ounce would matter. If not, then the discussion is moot.
If you wanted to do a real test, put them into identical covered boxes where you can't see them, then have a person hold them while blindfolded.
ZDnet claims 692g down to 654g, while TechCrunch says the difference is only 4 grams, and Hardware.info says the Surface 2 is 630g. The official MS website (going to UK since they use metric), the
official difference is: 676g versus "< 676g" In other words, it's negligible.
To say "lighter" in this case is more of a marketing hook than a significant difference for people who use on table/lap/keep in a bag.
There are still specific advantages for RT; price, IE10/jailbreak (without 8.1) being the biggest ones. If a college student is worrying about price, then the RT gains more value.
Weight is a big deal to me. My surface rt starts feeling like a brick after awhile.
Honestly, your best bet is to find an MS store and do the test I said above (or play around with both significantly--not sure they'll let you pick it up). I'm not convinced the differences are that significant when the OFFICIAL specs don't call out the weight loss in a meaningful way.
Edit to add:
You said nothing about your use case or priorities, but if you want a Windows RT tab specifically, there are other options (though discontinued, so that could be a problem), and Nokia is releasing one but I don't know the details. There are also other Win8 tablets, some of which are lighter and smaller. Then the usual iOS/Android options.