What is the difference between 井底之蛙 and 坐井观天? To express a person that has a narrow view, there are two 成语. According to 百度词典:


坐井观天



  坐在井底看天。比喻眼界小，见识少。



井底之蛙



  井底的蛙只能看到井口那么大的一块天。比喻见识狭窄的人。


Both words include derogatory sense (含贬义). But for me both seem to be the same otherwise.

I tried searching in Baidu, but could not find any trustful answers (example: this and this, etc...). Also I can't know which answer is correct or not. 

So is there any difference between these two Chengyu? For example is there any situation that using one word is OK but not for the other? The actual example is very appreciated.
What you got from Baidu is correct.

井底之蛙: the key word is 蛙. Metaphorically, you can reference a person to a frog, being in the bottom of a well. For example, you can say to someone: 你就是井底之蛙！

坐井观天 describes one's behavior/vision. You can say 不要坐井观天 to exhort someone not to be narrow for his thoughts or vision.