Yellow gold is still the most popular choice for an engagement ring and the color everyone thinks of when someone mentions gold. Gold comes in various karats with 24 being the highest and most expensive. The higher the karat, the softer the gold becomes so 24 karat is not the best choice for an engagement ring.
The most popular karat to go for is 18 karat which is a good compromise between strength and percentage of gold in the ring.
White gold is a little more durable the yellow gold because white gold has a number of other alloys contained in it. White gold also contains a mix of silver, managenese, palladium, nickel and rhodium.
White gold is catching up in terms of popularity with yellow gold because it has a look of platinum which is more expensive and stronger again. When it comes to price, you will find both will be of the same price with the same gemstone setting.
What you need to take into consideration is if your skin is sensitive and reacts to certain metals. Yellow gold is best and least susceptible to causing irritants on the skin but as white gold contains other metals such as nickel, it can cause allergic reactions.
At the end of the day, it comes down to individual preference and whether you prefer a classic yellow gold or a white gold that gives the platinum look for around half the price.