In Disk Utility, what advantages do "read/write disk image"s have over "sparse bundle disk image"s? If I want a read/write disk image, then aren't sparse bundle disk images always the way to go? They start at 0 kb in size, and grow to accommodate whatever you add to them, and if you delete stuff, they don't shrink automatically, but you can run a command to shrink them manually to regain space.

So what advantages does a writable .dmg have against a writable .sparsebundle or .sparseimage?
From this blog post:


  A customized .sparseimage file can be made larger than the total capacity of the physical volume on which it originally resides.  While the sparse image volume will seem to make that capacity available, attempting to exceed the physical capacity of the underlying volume will result in a disk error: "ran out of space."


A couple of other disadvantages of a sparse bundle:


Since it's actually a directory containing multiple files, it can't be attached to an email, sent with DropSend, etc. You would have to compress it into an archive first (eg. Zip).
It's only supported from OS X 10.5 (Leopard) onwards, so if you have an old Mac running 10.4 or earlier, you won't be able to open sparse bundles created on newer Macs.