Opening a large can of worms...
In Britain where I live collectors generally use Stanley Gibbons catalogues.
In the USA collectors generally use Scott catalogs.

I use both.
I much prefer the SG standard catalogues (Commeonwealth Part 1 and Foreign Parts 2 to 22) to the Scott standard catalogues. I prefer the greater level of detail and the layout of these SG catalogues.
I much prefer the Scott standard catalogue to SG's "Stamps of the World". In this case I prefer Scott's greater level of detail.
However, I have all these (and also Scott Classic, Michel, Maury, Facit etc.) on my bookshelves and find a lot of benefit in seeing how different publishers describe the same stamps.
SG prices are too high for the British market and need to be taken with a pinch of salt. However, I'm used to that and am happy to use them as relative prices.
Maybe others can comment on how Scott's prices reflect the market in the USA (or in Canada or other countries).