Because of their shining white color, platinum and white gold appear very similar to each other. But, they both have their distinctive properties and unique features & specialty. They look beautiful in their own way. So, it becomes the matter of personal preference which metal to choose?
The following descriptions about white gold and titanium will guide you the differences between the two. So, choose the one that is best for your needs.

White Gold
Being an alloy of pure gold and silver and palladium, white gold can be 18kt, 14kt, 9kt or any karat depends upon the mixing proportions of the metals. Like, 18kt yellow gold is made by mixing 75% gold (750 parts per thousand) with 25% (250 parts per thousand) other metals such as copper and zinc. 18kt white gold is made by mixing 75% gold with 25% other metals such as silver and palladium. So the amount of gold is the same but the alloy is different. Previously, nickel was used in making white gold but now it is no longer in use as it nickel can cause reactions with some people.
Normally, for making white gold jewelry more beautiful, we coat with another white metal called Rhodium. It is a metal very similar to platinum and Rhodium shares many of the properties of platinum including its white color. The rhodium coating makes the white gold look whiter. However, the natural shade of white gold is grayish in look. It also makes the white gold more strong and durable.

Titanium
Unlike white gold, titanium is used in its purest form to make jewelry. Because of its purity, it is extremely durable and long wearing. This grayish color metal is very lightweight, much lighter than a gold ring. Being 100% hypoallergenic, titanium has a unique property to be colored to bright colors such as blue, purple and black.
But, titanium cannot be used to make a prong setting for an engagement ring as it can not be soldered. That is why you will see that many titanium rings have parallel bands rather than tapering bands and why you will not see titanium rings with prong settings. Generally less expensive than 9kt white gold, titanium jewelry can be higher as the labor cost involved in it is really high. Though, white gold will still normally command a higher price than titanium. Choosing a metal is totally depended upon the personal preferences of the person. Pick the one that describe you more as a person and reflect your taste and style.