Both languages have those Chinese characters, called Kanji for Japanese. A meaning and a sound are associated with a sign with no information on how to pronounce it. This must be memorized for achieving a high level in the language.
Fortunately, both have a phonetic alphabet. The Chinese Pinyin was officially adopted in 1979 and uses the Latin alphabet. This makes the Mandarin language easier to learn for foreigners.
Japanese has 2 phonetic alphabets: Hiragana and Karakana. New learners must learn them – this makes the language learning challenging and funny. Another phonetic based on the Latin alphabet (Romaji) makes it easier to learn the first words.
VocaBattle contains some quiz that mix the alphabets and help a quick immersion in the language. For example, for the word とり (“tori” – bird), the とり<-> bird association won’t be asked in the easiest level, but there will be some quiz for associating とり with “tori” and another one “tori” with “bird”. The entry level is low and the alphabets become quickly familiar.
In Chinese, the first VocaBattle levels only use pinyin. The focus on the speed and on the score makes the regular repetition entertaining. The resulting reflex memorization is an advantage for students having the translations coming instantly in the head during a course or during a live conversation.
So, back to our main topic: what is easier, Chinese or Japanese?
The big difference is indeed the pronunciation. Chinese have phonetic tons, which makes a syllabus such as “ma” have different meaning depending on the way you pronounce it!