There are a ton of reasons why people choose to invest in gold and silver. Here are a few:
This decision will depend on your budget and your desire to transport your bullion. One ounce of gold will cost roughly 90 times the cost of an ounce of silver. This can be a blessing and a detriment.
Gold is comparatively expensive. As of June of 2019, a gold one ounce coin (about double the size of a quarter) would be roughly $1450. This means it is extremely transportable. $100,000 of gold easily fits in a pocket or a purse. The detriment to this is you must sell $1450 dollars at a time. If you need $300 dollars in cash, you cannot trade in 1/4 of your coin.
Silver is comparatively inexpensive. As of June of 2019, a silver one ounce coin (about twice the size of a quarter) would be approximately $16. This means that it grows in size quickly. $100,000 of silver would be 6,250 ounces and 13 large boxes and would weigh more than 430 pounds. The benefit is that you can sell and buy individual pieces. For $16 you can buy an ounce of silver or sell it for cash. It makes it easily divisible.
For most people, diversifying into both makes a lot of sense. It provides the means to liquidate some, while also keeping down on storage size, weight and the overall bulk!