I am not sure what is harder: learn separate characters for words or learn the correct spelling for words? Especially with English where there is a big gap between spelling and pronouciation, learning the correct spelling for words takes a lot of memorization effort.

The fact that many adult cannot spell 100% correctly, proves that spelling is difficult.

Writing a language is always harder than reading. Many people rely on muscle memory when writing words. It might be that this works better for writing chinese characters than for words, which is more likely to fail when words contain multiple instances of characters.

It might also be the case that the number of strokes needed to write an average characters is about the same as writing an average word.