how difficult is japanese compared to mandarin?
 

i took some mandarin classes at university and i found them to be ok. how much more difficult is japanese?

I think it depends on what language(s) you speak/have learned...
English may be easier than Chinese for German native speakers, and Korean may be easier than German for Japanese native speakers...no?

I did learn Mandarin for some time (I'd say my level is past beginner) and I can reassure you that Mandarin is a piece of cake compared to Japanese in so many levels. Japanese grammar is complex, Mandarin grammar is as difficult as English grammar to give an idea.. Japanese pronunciation is hard: I find some sentences impossible to say because they are like bloody tongue twisters, the tone/pitch accent is another struggle that will always make you sound as if you've lived in Japan for a week only. Mandarin has the tones, that once mastered (without exceptions), you can speak as fast as a mouse even in some cases, passing for a native. Writing... Japanese has traditional kanji plus lots of readings, Mandarin uses simplified kanji and they have one reading (there are very few that have more than one reading as far as I learned). All in all, Japanese is faaaaaaar more difficult, challenging and learnable in my expierence.

I think Chinese grammer is easier than Japanese.
But Japanese pronounciation is easier than Chinese. I think Chinese pronounciation has more variety, and some sound is really hard to pronounce for me (Japanese). Plus, the 4 tones....
I think Chinese polite form is not as nearly complicated as Japanese one, you can talk to teachers and friends in almost the same way, where in Japanese that won't be the case.
And in Chinese maybe there are more words you need to memorize newly because they translate foreign words like spoon, fork, ski, icecream, download, etc... but in Japanese you just need to know our accent for those words.
Well, I didn't learn Japanese as a foreign language, so it's hard for me to say which is more difficult to learn... but I learned Chinese for three years and found it pretty hard. (although I originally thought it's gonna be a piece of cake since I use Kanji as Japanse... of corse reading is easy for me, but still...)

My experience as a native English speaker is that Chinese grammar is easier than Japanese grammar for a native English speaker (but not by much and therefore should not be considered in choosing a language to learn), but that the writing is more difficult.

I also think tones are a relatively minor part of Chinese difficulty. English pretty much has three of the tones as well, but not used as tones per se. But the sounds exist and are therefore easy to use. Rising tone = English question ("what?"), falling tone = English command ("LEAVE!"), high tone = English singing ("la~").