I think it depends on your tone and whom you are calling " 傻瓜“ or "笨蛋”and what kind of situation it is. it either could be a intimate way or a rude way, really depends, but you have to avoid to use them if you can't handle them well, sometimes it would be a hurt when you say any of them.

Neither.

Thanks everyone~~~ ^^

lol~~~ haahahhaha, you mischievous girl... they all are very polite to use~~~ maybe all of them, you input them into your dictionary~ in english, are bad words, and you, of course, thought, the meaning of chinese characters that computer output is bad, unpolite. and you can use them to express your friends as a cute,interesting joke~~~ at least, you can call me, when I have a bad reflex, or make some mistakes hahah~~~

i think 笨蛋 is more lovely than 傻瓜. 笨蛋means someone doesnt or cannt finish work well 傻瓜mean someone foolish