[mistwang]

yes, httperf is better in this regard. However, httperf does rate limiting, not like "ab" sending request as fast as possible, so, httperf may report lower req/s than "ab" if the rate limit cannot push the server to 100%.

Opcode cache will help for all web servers.

There are other respects need to be taken into consideration other than the raw req/s, like server load, memory usage, CPU utilization, etc.