Here is one page that runs tests with RAID and a single drive…the real world results show that RAID 1 is frequently shower than a single drive, and when it is faster, it rarely is by very much
In any case, I don’t think the difference in seek time will be noticable for a home user. Maybe for a web server that’s loading thousands of little files per second, but not for a gaming PC where the disk-heavy tasks are more likely to be loading/copying occasional large files or swapping processes. Throwing in another 512M or 1G of memory so the system won’t have to touch the disk as much will have a much bigger effect, IMO.
That’s seek time per block, and even a small file is composed of thousands of blocks, so it adds up. It could be beneficial for loading large gaming maps.
But like you said… aside from this byplay over which flavor of RAID is better, I’ve gotten away from my original point that for home users, cost/benefit does not favor RAID for any reason at all. There are better places to use the cost of a second disk than to throw it away on backups.