On the PC storage side I just recently went from NTFS compressed ISOs to scrubbed (Game partition only) WBFS and saved a ton of space even with no compression on the WBFS files.
The only problem with WBFS is that it doesn't compress very well since the data is still encrypted. However, you can use Wiim's ISO Tools to compress them to WIA format, which is like a scrubbed WBFS file but with the data decrypted and compressed. The space savings are massive. The only downside is that the format is for storage purposes only and you can't run them directly with any loaders. You can easily convert them back to WBFS, though.
In any case the best format for actually playing them is scrubbed WBFS on a FAT32 drive with 32KB clusters.