Arabic isn't all that logical. It's like Latin + nonsense. There's a masculine and feminine form of every word, in almost all forms (most annoying being the possessive and plural). Even colors have a masculine and feminine form.
ex: za'hari(pink, masculine), za'haria(pink, feminine), az'rak(blue, masculine), z'raka(blue, feminine).
The writing system isn't so complicated; the diacritical markings help things make a bit more sense. Things are also spelled/writing as they're heard. But, there are the letters/characters that sound almost EXACTLY the same. Dha, da, theh, teh, gha, kha, etc. They can make spelling words confusing, especially if you have hearing problems.
The noun/verb "pronoun attachments" (that's what a friend that speaks Arabic calls them) are also sometimes complicated. For example, the word for "I" is "ana". So, to say something like "My book", you'd attach "ana" to the end of the word. Except it wouldn't be "ana", it'd the yeh character.
It would look like: كتابي; not that you would know how to read it, but it says "ketabi", the literal meaning being "book I", which is (not so) obviously interpreted into "my book".
That's my opinion on Arabic. (Sorry. if it's a boring or inaccurate read - I haven't gotten much sleep)
I think Japanese is more logical. The whole language is spoken and understood by context or situation. I also believe the writing system is perfect (kana); syllabaries make it so that the syllable only has one pronunciation. There is an exception for the 'g' consonant, but I think that's it.