No, it is always faster to add in the beginning (except that
add-to-list has to scan the whole list anyway - as pointed out by @phils in a comment).
However, performance is never an issue with
add-to-list which is only used to customize user options like
The reason to add to the end of an alist is to avoid disturbing existing settings.
E.g., I had
(add-to-list 'auto-mode-alist '("\\.ts\\'" . js-mode) t)
js-mode (actually, Emacs uses
js-mode for now but you got my point)...