If it is unclear to you what decompilation can offer on top of disassembly, have a look at the following comparison pages:
- Here’s what decompilation looks like, compared to disassembly.
- In a similar fashion: decompilation of an ARM executable.
- In a similar fashion: decompilation of an PowerPC executable.
Just for the record, here are a few pages comparing the output of the decompilation, across decompiler versions: