(I don’t speak Chinese, and I only know the basics of Japanese, so take this with a spoonful of salt.) Chinese seems far more difficult to pronounce than Japanese. In terms of writing, while hiragana and katakana are used everywhere in Japanese, they are only about a hundred characters out of the thousands of kanji used on a regular basis (and the thousands of less common ones), so knowing them won’t help much in learning Chinese. AFAICT, the simplified Chinese characters seem easier to remember than kanji, but it still seems incredibly difficult to learn (I’d love to be proven wrong, though). I assume the radicals (“sub-characters” used to compose actual characters) are simpler in modern Chinese, but I can confirm that remembering kanji and their pronunciation(s) is a massive pain in Japanese