I agree~when they both mean sth looks like:
他貌似某某明星。Here, 貌似is short for 相貌相似
他好像某某明星。好像 at here is shorten from 长的好像
(above sentences have the same meaning)
however, I think in Taiwan, 貌似 is actually much more formal than 好像。
I said it is a kind of teenager language. Almost every universtiy (maybe also high school, middle school bla bla bla) student can understand at least, but papas and mamas don't use it.and 我還是很好奇上海人會用"貌似錯"嗎?
這些在台灣都是很少聽的用法呢~这貌似不对, 我貌似喝多了, 这次他貌似考得不好
這看起來不對, 我似乎喝多了 are used in the same way as "官话" , but in "大陆", "這次她很像考的不好" is never heard. 如果我们肯定说"这次她好像考得不好"在台灣我想我們一般都講:這看起來不對, 我似乎喝多了, 這次她很像考的不好~ and all these may be replace by 好像, but 貌似 here sounds weird for a Taiwanese's ear.