Previously, I posted about free software.
There are just a couple of not-too-expensive commercial offerings that I think are excellent.
Beyond Compare 3 Pro
(File and Folder Difference Tool)
Available for Windows and Linux.
A single user licence for the Standard edition on one platform is approximately $30 (c. £20), and the Pro edition on dual platforms is about $80 (c. £50).
“A single user license covers one person using BC on any number of computers, or a single workstation accessed by multiple people.”
(quoted) [disclaimer: the wording and conditions are obviously subject to change by Scooter Software; this quote might no longer apply]
Hex Editor Neo
(Binary File Editor)
Available for Windows.
There is a Free edition, which is more basic than the other editions, but is still very good.
A regular, commercial, single-user licence for the Ultimate edition is around £65. A non commercial Standard edition is around £16.
<HHD Hex Editor Neo> (includes the main prices)
For the non-free editions, note that:
“One registered copy of the software may either be used by a single person who uses the software personally on one or more computers, or installed on a single workstation used non-simultaneously by multiple people, but not both.”
(quoted) [disclaimer: the wording and conditions are obviously subject to change by HHD Software; this quote might no longer apply]