Dear Grammarians:
Even though I have not conducted a scientific study or an official survey, experience tells me that a “Westerner” should answer that, undoubtedly, Chinese language is more difficult to learn than English. The reason for this answer surely lies in the vision of Chinese characters, so inscrutable without a minimum knowledge of Chinese writing.
However, if we look at phonetics, the pronunciation of English sounds is so complex that not even native speakers are able to learn it actively or metalinguistically without some difficulty. English is a language spoken in multiple countries and, in each of them, the pronunciation of the phonemes is different. For someone who learns English late, let’s say, in childhood and teenage age, it will be impossible to speak the language like a native, almost entirely due to this complexity of its phonetics.
However, Chinese language, phonetically, is very different. On the one hand, there are just over 400 combinations of consonant + vowel [+consonant], that is, there are only about 400 syllables in Chinese. For example, the morpheme “san”, “da”, “qiu”, etc. If we are able to integrate this number of syllables into our phonetical system, we will have almost won the game. Those who defend the greater difficulty of Chinese will argue the existence of tones. That is true. In Chinese, there are four tones plus one neutral tone, and the difference in pronunciation between one tone and another implies a change in meaning.

However, it should be borne in mind that standard Chinese (the one currently spoken throughout the PRC and also in other parts of Asia) tends to disyllabicism, that is, most of words used are disyllabic. For example, “cup” is 杯子 (beizi), while “eat” is 吃饭 (chifan), and “dad” is 爸爸 (baba), and so on for a few thousand more words. This is an advantage for those who do not master the tones, because, even at the risk of pronouncing them incorrectly, the fact of pronouncing words of more than one syllable greatly contributes to their understanding, since it is easy to misunderstand the pronunciation of a word when it only has one syllable or one character, but it is difficult to misunderstand a complete sentence even if the tones are incorrect.
We hope we have demystified a little bit the difficulty of learning Chinese. If you are interested in learning Chinese language, you can go to numerous reading sources and also take Chinese classes, adapted to your level, availability and schedule.
See you soon!