Thanks for asking,
RP Cram Notes: 44 pages (paperback) 45 pages (kindle)
NUF Cram Notes: 116 pages (paperback) 250 pages (kindle)
RP cram notes covers 96% of the testable material, NUF covers 100%.
RP Cram notes does not mention "canned detectors", or F-18. NUF does.
RP cram notes is aimed at the guys that have taken the test countless times over the last 30 years, and is intended to be as little as possible. NUF cram notes expands on some sections that people had difficulty with, like the math.
NUF cram notes lists the 50 objectives the test covers, then the critical info for that objective. The RP cram notes just has the critical into, without listing the objectives.
NUF Cram Notes has more pictures!
NUF Cram Notes has some info about ANSI standards (18.1/3.1), acceptable experience, resume tips, history of NUF, etc.
NUF cram notes also has a section on meter reading!
The Kindle version also has ~ 135 additional pages of glossary of nuclear terms. I tried to put that in the print version also, but it doubled the price.
The NUF Cram notes is the RP cram notes on steroids, in development for 30 months based on customer feedback on the original.