I find Spanish a much easier language to learn.
I studied Chinese before going to travel overseas and it was one of the most difficult things I have ever done. I learned Chinese from a lady who was from Shanghai and then went to rural NW Yunnan. Yeah. Although the characters are the same, there are so many different dialects in the country. No one understood anything I said - I was a Canadian girl trying to speak with a Shanghai accent apparently. They put the character subtitles on pretty much all of the television programming there for that reason, so everyone can follow along, because the characters for the words are always the same. And even my Chinese friend, who was born and raised in NW Yunnan, travelled with me to Southern Yunnan and had difficulty communicating with the locals.
Therefore, I vote Chinese, simply because I feel it is more difficult to learn on your own and you'd benefit from having a real teacher. It would be much easier for you to brush up on your Spanish on your own.