[TYDS]

#define DIALOG_TEST 0
.......

or
enum
{
DIALOG_TEST
}

[Vince]

Just use the enum. Don't even bother comparing speeds because the difference will probably only be noticeable after a million iterations, if at all.

[CheezIt]

Neither. You should use '#define's if you'd like no character limit for the elements' name. If that limit doesn't bother you however, then the enum would be your perfect choice (you won't need to manually define their values).

[Yousha]

Usually dialogs are sorted... Enum is better.