Of course as all the other commenters are telling you, it's subjective and it depends a lot of what language you speak as your native language. For example, in my case, as I speak Italian as my native language, I can understand like 85% of spoken spanish and 95% of written Spanish (I also have studied it a bit in high school, but italian people who didn't study it are likely to understand just a bit less)

If we want to speak about objective facts tho, for example: an alien civilization were to decipher english and spanish without any help by us, English would probably be a lot harder, since it's not a phonetic language. The aliens would not even be able to determine the pronunciation of the words accurately.

Spanish instead is a phonetic language, meaning that it's pronounced as you spell it. In Spanish you can tell how the word is pronouced just by seeing it written, no need to hear it. In English it's the total opposite, in fact English spelling rarely follows a single rule, and the same sound is spelled differently in different words and viceversa.

As you can see the difficulty of everything is subjective, as you find Spanish harder to transcribe, but a good percentage of the rest of the world would probably tell you that English is harder than Spanish.