There are a lot of people who don't own widescreen televisions and for those cases, letterbox will be ideal. Your claim of non-anamorphic material being "always inferior" is a simplistic and somewhat naive opinion.
I'm trying to say the image being letterboxed has nothing to do with 16:9, 4:3 or anamoprhic.
I'm also trying to say an 16:9 image (whether or not anamorphic) can be viewed in the right aspect ratio on a 4:3 tv, but a fullscreen image ( in this case 4:3/fullscreen, 2.35:1 letterboxed) can't be viewed in the right aspect ratio on a 16:9 tv. So go for 16:9 anamorphic, then everybody can view it in the right aspect ratio no matter their tv.