10 Karrot gold also will not tarnish for years?
In order to keep gold white and luster-full, the gold is coated with rhodium. The rhodium will fade over time and the ring will loose its luster. There is the option of getting 10k gold and taking it to your local jeweler every few years for a rhodium polish.
Otherwise i would stick to platinum as its shine will never fade. Also if this ring will be hosting diamonds or other stones , platinum is known to hold them in place most securely.
Also, if you specify what type of ring you are looking for , i may be able to point you in the right direction price wise.