This is an excellent question and we hear it almost everyday.  Before you make a choice on platinum or white gold it is best to understand the differences in the two precious metals.

Platinum: Platinum is a dense white precious metal that is use to make jewelry.  Most platinum jewelry pieces that are made and sold are engagement rings and wedding bands.  Platinum is a bit stronger than gold in its raw form and does not need to have a great deal of alloy metals mixed in to make it into wearable jewelry. Platinum is also a hyper-allergenic making it a great choice if you are allergic to gold. Most platinum pieces will be marked with PT 900 or Plat 950.  This is to notify the quality of the platinum in the piece.  The mark 900 simply means 90% platinum and 10% harder alloy metal to make the platinum a bit stronger than 100% pure platinum.  950 means 95% platinum and 5% harder alloy metal. Platinum polishes beautifully to a bright white silver finish.  It is also very malleable much more so than 14k or 18k gold.  It makes a great metal for setting diamonds as the prongs bend easily to hold the diamonds and gemstones. Platinum does scratch very easily and after wearing platinum for a bit it tends to get dull.  To fix this dullness it can be polished back to its luxury finish and look new again.  It does take a bit more time to polish than gold.

White Gold: White gold is not actually white. It is yellow gold 24k that is mixed with white alloy metals to make the gold appear white.  There is no way to make it completely white so it will always have a slight yellow tint.  To fix this issue we Rhodium plate the gold with a bright white finish that can last from a couple months to a couple years depending on the acidity levels in your skin and how you wear your jewelry.  Once the rhodium wears of gold is still holds a luster and more so than worn platinum.  Also, you will see a slight yellow tint to the gold once the rhodium wears off.  To fix this jewelers can easily polish and rhodium plate the white gold to bring back the bright silver finish and make your jewelry look new again.  Straight from the ground gold is usually 24K meaning it is 100% gold.  At this stage it is a rich bright yellow.  It is soft though and not really strong enough to hold diamonds and make jewelry without bending or losing stones.  Gold is mixed with harder alloys to make it ready for jewelry making.  You often hear the quality of gold as 10k, 14k, 18, and sometimes 22k.  This is stating the percentage left of gold after mixing in the alloys.  10k gold is 10 parts gold 14 parts alloy metal adding up to 24k.  If you divide the percentage 10/24 it equals 41.67% gold in the finished 10k gold item.  10K gold is not even half gold.  14k gold is 14 parts gold 10 parts alloy metal.  14k gold is 58.33% gold.  18k gold is 75% gold.  The higher the gold content in a piece of jewelry the more it costs.  The lower the gold content the lower it costs. The benefit to lower gold content is that gold strengthens with lower purity.  A 14k gold ring will be stronger than 18k and hold up better over time.  Some people can be allergic to gold.

Which one is stronger? Gold or Platinum

Straight from the ground pure platinum is stronger than pure gold and is also more dense. However once the hard alloys are mixed with the gold 14k gold becomes stronger than platinum.  If you had two rings of equal volume one being 14k and one being platinum, the 14k ring would be stronger and lighter than the platinum ring.  If the 14k ring was white gold and rhodium plated there would not be away to visually tell the difference.  The only way to tell would be to feel the weight or test.  The platinum would weigh more.  After the rings are worn a bit you would also be able to tell the difference.  The platinum would dull to a grayish color and the white gold would lose its rhodium finish and you would see a light yellow tint.  Both can be made to look new again. 

Which one costs more money? Gold or Platinum

In jewelry platinum costs more than gold.  Many times we get asked why?  Gold is worth more an ounce than platinum why should it cost more? The reason for this is that the combination of purity (platinum 95% pure) (gold 14k 58.5% pure) and weight difference (platinum is more dense than gold) causes platinum to be more expensive to work with.  Many jewelers over the years have told consumers that platinum is better simply because it costs more giving them a higher sale. It is not necessarily better.  Platinum is best for people that are allergic to gold.  If you want the most bang for your buck the best metal to use for your jewelry is 14k.  It is stronger and less expensive.