Colour
Platinum is naturally a silvery white metal which requires a very small amount of maintenance. It only requires a polish to bring the lustre back. It does not tarnish like silver and white gold.
White Gold is naturally yellow, it is then mixed with other alloys, finally it is coated with a layer of Rhodium, which is white & comes from the platinum family. Over time & wear, the ‘whiteness’ does dull and and slowly turns yellow, therefore it does need re plating to bring that white finish again like when you first got the jewellery.
Strength
Platinum is a rarer metal than white gold & less malleable due to its density.White gold is not as dense, however it is harder, so it does not scratch as easily.
Allergies
One big benefit platinum holds over other metals is that it has no nickel, which some people may be allergic to.
White gold contains nickel traces.
Price Difference
Platinum is a more expensive metal overall even though per gram gold has the upper hand. This is because 18ct gold rings have only 75% purity, whereas platinum has 95% purity.
White gold has a mixture of metals, therefore it is more affordable.
Weight
Due to the density of platinum which is over 50%.. It is definitely more heavier than white gold.
White gold is lighter as it is not as pure as platinum, so this may be a better choice for those who are picking larger rings, or rings with just a lot more total weight.