Platinum is most couples' first choice in precious metal. Its steely white color won't change over time, and, because it is more dense and malleable than gold, the prongs are more likely to resist injury. Platinum engagement rings are the ultimate. Their weight, feel and durability is unsurpassed. While over time platinum will take on a brushed, antique look called "patina", it can easily be polished to look new. For most, however, the patina speaks to quality and is part of platinum's unique and timeless appeal.
18K white gold is rich, lustrous, and is always used in finer designer gold pieces. It's also more affordable than platinum, and for gold purists, it is the only way to go.