Neither are appropriate for cyclocross, triples being too glitch-prone for racing. Last couple of years one sees more single front rings. As a general use bike though, 631 frame w/ 105 levers and RD beats 520 frame w/ Tiagra. A few years ago, you could buy "last year's" Nova for $700. Now, it's as expensive as a Poprad, I think, so I am thinking, go Poprad. Tell me if you see the Nova for significantly under list somewhere. Now that the Poprad went to 105 it is much improved, its 853 (or whatever it is now) frame superior to the Nova's 631. I don't really trust the new Poprad's paired spoke wheels though. As far as investment, bikes are poor investments, though not as bad as cars. Value is another question entirely, a fine bike has enormous value.
the 04 nova im looking at is $899 (yeah i know, an 05 is only $150 more!)...i'm waiting for it to go down to $700. i think "investment" was the wrong word to use. i just wanted some more opinions on the bikes.