Sometimes I am asked which metal lasts longer 14k, 18k or platinum. The real answer to this question depends upon a number of things but all other things being equal (type of construction, etc) platinum generally last two to three time longer than gold. When alloyed with Irridium, platinum is more durable and it also has perfect resistance against chemicals found around the typical household such as chlorine found in tap water. Generally speaking settings made 100 years ago out of platinum are in better condition then a similar setting made of gold.
Interestingly one would think that 18k contains more gold than 10K (75% vs 41.6%) so it must be softer and wear out faster. Tests have shown this not to be the case rather the 10k is so heavily alloyed that it tends to be more brittle and not hold up over time as well as an 18k setting of the same type of construction.
In terms of construction sometimes two settings can look very similar but be significantly different in terms of durability. More on this later.