Well, servers typically care about throughput and not latency. So if your ARM server will process 10000 requests per second with each request taking 100 ms and your x64 server will process 8000 requests per second with each request taking 80 ms for the same price, ARM will be preferred. There are exceptions, of course, but generally server workload is an ideal case for multi-threaded applications, because each request is isolated. That's why server CPU's usually have a lot of cores but their frequency is pretty low.
