I just read a post entitled Some Men are Fools where the writer talks about her boyfriend asking her whether or not she wanted white gold or silver in an engagement ring. I have known women who have had both. The disadvantage of silver is that it tarnishes, and it takes some work to keep it polished. White gold still has to be dipped in rhodium — a platinum derivative — once every year or two. Silver also must be dipped in a different blend of rhodium. If the silver is anything less than 925 silver, it will melt when it is dipped and it will bend.
Since marriage is supposed to be forever, and because you wear your engagement and wedding rings every day, white gold or straight platinum is the best way to go. You can always save money by putting an artificial (yet beautiful) stone, like enhanced Moissanite or cubic zirconium, in the center setting. Later, you can replace it with a real diamond. Trust me on this — no one will know the difference.