Sell the Bianchi.
it is newer = you'll get more money for it. (would you feel right selling your 520 in uknown condition to some poor schmuck?
)
it is a Bianchi and Bianchi-colored = more likely to get stolen.
you are worried about scratching it = unsuited for commuting
use some of the $$ to rebuild the 520. maybe spring for fresh drivetrain & wheel rebuild.
my 2 cents, lemme know if yuo want change
