I do not know what you mean by a "4 claw eternity band" but I can
give you my opinion on the differences between the two since we do a
lot of wedding and engagement rings. ( 98% of them platinum.)
18kts. is extremely BRITTLE due to the nickel content and has a
greater tendency to crack more easily than platinum, which is
extremely SOFT and mushy due to it's purity. An analogy between the
two could be platinum is soft like butter vs. 18kt. white is hard
like a brick. 18kt. white does not give, platinum will squish.
A ring made from platinum will outlast any 18kt. ring by decades.
That is why there are so many antique platinum rings in estates
today. Wouldn't your customer love to pass her ring onto her heirs
for future generations to admire? Although their is of course a
large difference in price, platinum over time will be the better
investment. Just my 2 cents...