The Gibbons is still more detailed than the Scott Classic, though the latter is catching up. In recent years, the volume you speak of went up to 1952 so all issues of King George VI were included vs. Scott only extending up to 1949 issues. Newest volumes now go though 1970. Older Gibbons catalogs work just fine; see
Amazon or
ebay and don't order from someone using cheap plastic mailing bags. The books are too heavy for them.
Sets can constructed differently vs. Scott and color/colour names are different. If you are moderately good at using Scott, you should have no problems.