Here you can see the minimum and maximum transfer performance of all configurations in one single chart. The four drive, four channel setup is indeed almost four times faster than the single DTLA.

Disk Access Time

It was predictible that the access time would not be quicker in a stripeset. Though the data throughput is considerably higher, the drives cannot possibly position their heads any faster. This not only applies to software RAID, but also for all kinds of hardware solutions. Expensive adapters may have RISC controllers with a lot of cache memory and sophisticated algorithms, but they cannot solve the basic problem. Conclusion: If you are running demanding applications that frequently access data bases (e.g. a webserver), try to get drives that have quick access times.