Well, in my opinion, English is hard to pronounce (for example, it impossible to know to to pronounce the word 'live' without context) and French is hard to spell.

Since you mention the /eɪ/ diphthong, in French it can be spelled é, ée, et, ed, er, ai, and many others. What is making the French spelling harder, I think, is that many letters are not pronounced, and some words have the same pronunciation with a different spelling (for example: cou - neck - and coup - hit). I can't think of anything in particular, but it all lies in the fact that many letters are not pronounced. I found this website - in French - where you can have fun testing your French spelling: http://timbresdelorthographe.com/