>大阪は食べ物が美味しいです You think it is weird because you might regard the function of "は" is "the marker of subject". Then you might wonder, what would 'が' be? Two subjects in one sentence? Maybe you think the gramatical structure of "大阪の食べ物は美味しいです" as: "大阪の食べ物" is "美味しい". However it is not, though it looks like so. The particle "は" fuctions as the marker of "theme'", or of the literal meaning of subject, "a thing thrown('ject') to under ('sub') ". It is called "theme", base of a conversation. If I translate these, emphasizing gramatical structre. +++1．"大阪の食べ物は、美味しいです" -> Talking about "大阪の食べ物", it is "美味しい". +++2．"大阪は、食べ物が美味しいです" -> Talking about "大阪", it is "食べ物が美味しい". or you can say +++3．"3年前、はじめて大阪にいったときいちばん感動したのは、食べ物がメチャクチャおいしかったことです" -> Talking about "3年前、はじめて大阪にいったときいちばん感動したの（＝感動したこと）, it is "食べ物がメチャクチャおいしかった". +++4: 「大阪は、大好きです／きらいです」 -> Talking about "大阪", it is "(I) love /hate it". All four lines share the one gramatical structure, "Talking about A, it is B". For more explanation, refer to: https://www.italki.com/question/424283

What the both sentences want to say is almost the same but there is a small difference of nuance. 大阪の食べ物は美味しいです。 The food of Osaka is delicious. 大阪は食べ物が美味しいです。 I think it would be easier to understand with: 大阪は食べ物が美味しい場所です / 都市です。 Osaka is the place / the city where the food is delicious. I hope this helps you.

As I know there is no different between two grammars. But most of the time, I use the first one if there is only one characteristic of the subject. If there are two or more, I prefer the second one. 大阪は人が親切なくて, 食物が美味しいです