🚀 go-pugleaf

I've evaluated and seen a lot of compression products... here are some
of the things that came to mind on each...

1) More Disk Space 2.0 - uses resource compression on apps and can
optionally make them run compressed on workstations without MDS
installed (although a little box appears with Alysis Software's name in
it).  These apps tend to launch quicker though do not compact as tightly
as a more traditional method of whole file compression.  Their data file
compression/decompression is probably the fastest though a little less
tight than AutoDoubler 2.0 or SpaceSaver 1.0.1.  One of this products
biggest pluses is that the decompress INIT is installed in the System
file so that even if you disable INITs, you can still use compressed
files.  All in all, a great product in spite of a few minor bugs and
interface quirkiness.  Another neat thing about it is that you can
compress items in the System Folder since the INIT is in the System
file.  This extra space savings should be factored against its
competitors.  Never lost data with it.  With SuperDisk 2.0 (which will
include MDS), you can add a suffix to volumes, folders, and files to
make compressed.

2) Stuffit SpaceSaver - Great on compatibility, tight and fast
compression but tends to fragment the hard drive a lot.  Has the same
feature as SuperDisk/MDS for compression on demand via file/folder name
suffixes.  You have more control over what gets compressed if you have
the MagicMenu from Stuffit Deluxe 3.0. Even without this, there is a
much higher level of control than AutoDoubler for non-background
compression.  A newer version is supposed to be released soon that is
faster and tighter (free update).  Stuffit SpaceSaver CDEV/INIT uses up
about 250K of RAM when loaded.

3) AutoDoubler 2.0 - Comes with a few nice goodies like CopyDoubler and
the AutoDoubler Internal Compressor (AIC).  Use of the AIC can make apps
launch faster (and usable when AutoDoubler CDEV isn't loaded though not
on other machines without a license for AutoDoubler for legal reasons). 
Items compressed by AutoDoubler itself tend to launch faster that
SpaceSaver because of the decompression method used.  More potential for
problems with apps that are self-modifying (like store preferences
internally in resources) than MDS or SpaceSaver.

4) TimesTwo from Golden Triangle Technologies - Compression is done at
the SCSI driver and is therefore totally transparent to all software
except apps that bypass the SCSI Manager (a very small group).  While
this is the ultimate concept in terms of transparent compression in that
you could install their driver on a Syquest cartridge, your hard drive,
an optical drive, etc. and volumes on those media will tell you that
they are twice as large as they really are.  Unfortunately, while
compatibility is great, performance is not.  Every file that is written
to or read from a drive with their driver installed is automatically
compressed or decompressed.  Try using virtual memory or QuickTime on a
drive with TimesTwo and you might be a little disappointed. Also, since
this is not a compression utility, you can't compress files to be sent
to an online service or whatever.

I hope my impressions of these products are helpful to those who are
shopping around.  If you're also buying a hard drive, I would definately
recommend spending the extra hundred bucks for 100 more megabytes rather
than rely on a compression product.