I no longer have my copies of either guide for reference (lent and never returned alas) but both were editions that predated UT - and by the time I got to UT I needed them less, it was the Silmarillion and its many similar names that I really needed them for -.... so the difference was less marked...and I can't really remember them distinctly - save that one was a nice hardback and the other a huge and battered paperback.

WIthout them I use the encyclopedia of Arda or the HoME index.