Are ae and aeguill only needed when using CM fonts?

Question

I am using the memoir class with the option extrafontsizes so as I understood this uses the LM fonts and at the same time set the T1 encoding.

If this is correct, are the packages ae and aeguill still needed ? I think they are not.

Answer 1

The packages ae and aeguill are obsolete and should not be used anymore (ae consists in virtual fonts which fool TeX into believing it's using real T1 font). By using the package ae instead of a real T1 font, you won't be able to use the search functionnality of the PDF reader for words with accented characters like é, à, etc. Copying and pasting won't work either.

Instead, you should always use

\usepackage[T1]{fontenc}
\usepackage{lmodern}

(Of course, lmodern may be replaced by another font package and you may want to use another encoding than T1 for some languages.)

Answer 2

I can't think of any case where ae or aeguill are needed or useful today. Even if you don't use the lm-fonts: the cm-super-fonts provide type1-versions of the ec-fonts.