@Tori: that's kinda odd. I thought Kenkyusha was compiled by natives?
Are you sure that you're not overthinking this? Because yes, 向け is more commonly used. However, think about how にふさわしい or 適している is used. Think about how "suitable for" is used in English.
"This is a coat that is suitable for women". It says nothing about men and whether they can or can't wear it. (i.e. the NOT group is underspecified). It means that it's been designed to meet women's popular tastes, or that it's been tailored for a woman's body. There's no reason you shouldn't use "suitable" rather than "for", though yes, "for" would be a much more common choice here, just like 向けに is.
4 〔適すること〕 suitability.
●万人向きである suit all tastes
・輸出向きの 《toys》 for export
・夏向きの服 clothes for summer wear; summer clothes
・事務所向きの部屋 a room 「suitable [fit] for an office.
●小中学生向きに編集された新聞 a newspaper edited for the elementary and junior high school age group.
●…向きの for…; suitable for…; suited 「for [to be]…; to sb's taste
・家庭向きの女性 a family-oriented woman
・万人向きのデザイン a design for all tastes
・映画向きの小説 a novel suitable for making into a film.
●その柄は女性向きです. That pattern is for women.
・彼は商売向きではない. He is not 「very businesslike [business-oriented].
向き不向き
●人にはめいめい向き不向きがある. Each person 「has his or her forte [is useful in his or her own way].
・営業の仕事は向き不向きがある. Some people are suitable for sales and others aren't.
向き向き
●お客さまそれぞれに向き向きがあるのでよくお話を伺ってから商品をお選びしています. Everyone has their own taste, so we choose products after consulting with customers.
2 〈適していること〉
¶輸出向きの 《toys》 for export
・若者向きの雑誌 a magazine directed at young people
∥ここの料理の味付けは万人向きだ. The seasoning of the food served here suits all tastes.
2 《適合》
━[形] (…にふさわしい) suitable (for…); (人が…に適する) suited [P].
━[前] (…のための) for… 《指記号むく1; むきふむき》.
¶このコートは若い人*向きです This coat is for young people.
・彼はまったく政治家*向きだ He is particularly suited to be a politician.
*************************
(bound, headed) for….
●東南アジア向け綿製品 cotton goods for export to Southeast Asia
・海外向けの放送 broadcast 「for a foreign audience [to foreign countries]
・南米向けのラジオ放送番組 a radio program beamed 「at [on to] South America
・子供向けの科学雑誌 a science magazine (intended) for children; a 「children's [child-oriented] science magazine
・成人向けの映画 an adult movie
・独身者向けのマンション a singles apartment complex
・病人向けの食事 a diet suitable for invalids
・専門家向けに作られた製品ですから, 一般の方には不向きかと思われます. This product is designed for specialists and may not be suitable for the general public.
・大統領の演説は国内向けだった. The President's speech was meant for a domestic audience.
(bound [headed]) for
¶東南アジア向けの輸出品 export goods headed for Southeast Asia
・幼児向けのテレビ番組 a TV program directed at preschoolers.
━[前] (行き先・対象などが) for… 《指記号むき1》.
¶これは子供*向けの番組です This is a 「program for children [children's program].
**********************
Can you see the difference in nuance from these example sentences? Neither of them seem to suggest anything about the "not" group to me. It seems to be more of a difference in nuance than anything.
@Tzadeck: oh yeah!!! that makes more sense, i didn't think of that

perhaps it's in some Japanese accents, i dunno, but i've definately heard girls trying to be cutesy doing that with なくて.