Yeah, the most cache-friendly structure is going to win, but failing fast means no strcmp test if you happen to get a collision, which is potential miss to fetch the characters. And if the hash uses bucket chaining, the programming gods help you.

On an interview I was once asked to calculate the latency on a hash fetch in Java with the JDK String, hit and miss. It all basically boils down to how many caches misses are you going to have. I literally just counted up the memory accesses and counted up the hits and misses then gave an answer for cold and hot cache. Then we worked on rewriting it.