If you want a lot of different behaviors, go with Lua.
If your behaviors can be determined by some boolean (Aggressive, follows target, ... ...) go without.
Between the two I'd go without also (say 16 enemies and 4 bosses for example I'd hardcode all that).
My two cents are that scripting is usually for scripters, not for coders so if you feel comfortable with the language used, stick to that language, if you don't (and maybe you will want to add enemies months and months after the development was finished) you might want to go with a scripting language as it is definitely more secure than breaking up old code...
