I think lzx is great, it compresses better than lha and uncompresses much faster.
Yeah LZX gives best result for compression ratio but there are some problems - you may have some difficulties managing the LZX archives on other than Amiga platforms and it's not always faster. On my AmigaOne I use the PPC native version of LHA and it's much faster than the LZX's 68K emulated with petunia version, so it depends how multiplatform you really are.
As for whole disks I used DMS before but some Rob Northen computing protected disk may fail to archive with it, so I started to use TransADF with use zipcode switch (ADZ files), which are more easier to manage on different platforms and the compresion is almost the same.
