みたい・そう: the difference
みたいN4
Meaning
Seems; looks like; like
Past papers
Tested 5 times in past papers
Example
この犬は熊みたいです。
This dog looks like a bear.
そうN4
Meaning
Look like, Appear, Seem, Have a feeling that
Past papers
Tested 11 times in past papers
Example
雪が降りそうです。
It looks like it is going to snow.
How to tell them apart
「みたい」 and 「よう」 mean the same; they differ in style. 「みたい」 is casual speech; 「よう」 is written or formal. A noun takes 「の」 before 「よう」 (子供のような) but not before 「みたい」 (子供みたいな).
「そう」 is a quick impression from looks; 「みたい」 is a judgment from overall observation or from what you were told.