By standard and extended, I think (hope) you mean HFS and HFS+.
HFS is a 16-bit file system (correct me if I'm wrong) and can only have so many files per volume, and as drive size increases, so does the minimum allocation unit. This started to become a problem about the time that hard drives reached 1 GB. A 1 GB partition, using HFS standard, would have a minimum filesize of 16KB. That doesn't seem like much, but if a document only has 400 bytes of actual data, and you've got a lot of those documents (such as prefs files) then the wasted space adds up.
HFS+ is the solution to HFS. It's a 32-bit file system with a very high limit on files per volume (of like 6 trillion files, although it is still a limit). The real advantage of HFS+ is that it uses smaller allocation blocks, so that same 400K file would only take up 4KB as a pose to 16. There's still wasted space on tiny files, but a lot less. Other advantages of HFS+ are larger maximum file sizes, bigger partitions, and less fragmenting. The only disadvantage of HFS+ is that it won't boot or even work on 68K machines.
Hope this helps.