Well, practically I've been studying Japanese for 3 years in college. A few of my friends speaks chinese which they mostly learned about 5 years during schooldays. All of them said that Japanese is much easier as the characters(kanji, hiragana, katakana)
are much lesser and easier to be remembered. Well as for me, who only currently learning japanese, it is already very tiring remembering all these kanjis, so I could never imagined having to write hundred percent kanjis in essays and such when learning chinese. But that's only from the characters though. Not really sure about the grammars, vocabularies and others. Hopefully this helps!

Okay, now you guys are scaring me cause Im going to Uni soon and I will major in Korean and Japanese O.O
I can already speak/read Korean but will have to learn Japanese in Uni

AND chinese grammar is MUCH easier than japanese grammar
the chinese characters don't change because of a changing sentence structure, but japanese does

both languages need a lot of effort
people always say japanese is easier but they always forget that you have to learn (old) chinese characters for japanese too and the old ones are much harder than mandarin where you use the modern (short/easy) characters
I study sinology (chinese scienes) for years already and I know a lot who study chinese and japanese and all of them end up saying that japanese is not much easier than chinese at all, so don't let yourself get distracted by the fact that almost everyone says it's easier (just a tip)

Well to me, it depends on what you want to be in the future. What course do you take? Which language will help you to widen your career in the future? Nowadays many companies love to hire bilingual staff especially japan,mandarin and korean.

Japanese!!

I've heard that Chinese sentence structure is close to English or other European languages while Japanese is closer to Korean structure, for example. Chinese grammar is typically easier to learn. You don't have to worry about conjugating verbs and no language change based on gender, both of which Japanese uses heavily. Japanese is a lot easier to pronounce. It's not based on tone (Chinese), so if a mistake is made, chances are you'll still be understood.

From experience, it's better to have motivation and learn a hard language, than no motivation with an easy language. The language will seem hard if there is no motivation or reason to learn it. You already have interest in Japanese and have exposure to the language from anime. Those could be a good benefit to you!!

I had to choose a second language to study too, so I know exactly what you're going through!

Personally, I think Chinese is harder since there are pronunciations different from what I am familiar with. Although, it is a language that is more well-recognized (as well as Japanese) on the back of products as one of the many languages, it seems the letters/ are what makes Chinese so complex. I might say to pick Japanese because you're familiar with the language a bit since you're interested in animes. Their pronunciation is not exactly as tongue twisting and stressed to say certain words. It's more loose on the tongue, I believe? Can't really find the right word ^^''' I have friends who took Japanese and one is currently on her 4th year of Japanese as a senior and I can tell that it wasn't easy for her and my other friends who took the class. I was interested for the class when I entered high school but instead, I was switched over to French~ For Japanese, I do remember that kanji is the hardest to memorize and learn. My friends would sometimes complain about how kanji was too complicated for them when they had tests coming up. But the other styles of the Japanese words: hiragana and katakana, might be easier for them (was there only three?).

mandarin is definitely harder than japanese according to my friends who studied both. like some of my chinese friends who speak fluent cantonese struggled in their mandarin classes. i haven't taken either but i think japanese would be easier!