At The Eclectic Light Company blog, Howard Oakley writes:
Over a year ago, Apple changed the way that one of the most popular formats of disk image works on APFS. This article re-evaluates the more common general-purpose formats in light of that change. Now that plain disk images can be highly efficient in their use of disk space, should you make more use of them?
When creating disk images in Disk Utility, I’ve long wondered which format to choose. Howard Oakley has now done the Mac world a service by comparing the three main types—plain read/write disk images, sparse images, and sparse bundles—on space efficiency, performance, and convenience. Read his full article, but I’ll stick to sparse bundles whenever possible (and plain read/write disk images when not).