) I'll share my story just as an example, maybe it will help... maybe not.I started with Mandarin in 2012 when I was a medical student. I moved to NYC in 2011, and having learned Spanish to an intermediate B2 ish level at that time really paid off, and immediately was useful, and since there are several Mandarin communities spread out throughout NY, I thought it would be best to dive into Mandarin. At the time, I wanted to learn a non European language for a long term challenge and commitment. I initially wanted to learn Arabic, but the practicality of Mandarin here was greater, so I went for it (I'd still love to study Arabic some day, but I'm spread too thin as is). I was enthralled by the difficulties, not intimidated, and I wanted to see how well I would fare with the writing system, the tones, the history, and a language and culture that is completely foreign to me. I started with a free beginner Mandarin course for students that met 1 hour once a week for 8 weeks, and I bought the Assimil Mandarin with Ease, Pimsleur I-III, and watched "growing up with Chinese" (eventually that got slow and boring, never got through that), later on I also listened to all beginner podcasts released by popupchinese, which are humourous and fun, not always the most practical language but since they were often funny (to my sense of humor), vocabulary seemed to stick. I also did other things from time to time. Granted I have been busy, but that is what I have gotten through since 2012, I put in somewhere over 500 hours (probably in the range of 700 if I had to guess), and I would say I am an advanced beginner. I can have a tutor session for an hour and have it be mostly in elementary Mandarin, I can read basic things for beginners, but any true real-life use of the language still escapes me. There is some practical use, I know enough Mandarin that I can introduce myself well to patients, do a physical exam when away from the interpreter phone at the hospital, and give basic instructions (your medicine is at the pharmacy, you need to have your blood drawn now, go to clinic blah blah for radiology) that I have learned, but for all true conversations I rely 100% on interpreter services. I honestly have not found Chinese media that I can say I enjoy to just passively get more exposure to the language, and I still have to force myself to study. I do this more out of love for language learning, which sometimes can feel like a chore, but I am in a habit of doing it, so that helps me to continue my slow climb up Everest.
I never had a cultural interest in Japan growing up. I wasn't opposed to it, and if I had more exposure, I likely would have enjoyed it, it just wasn't on my radar. I also knew no Japanese people, I grew up in Iowa, didn't have much exposure to Japanese culture or cuisine, so I never thought to study the language, hence my first choice of Mandarin. In 2014, I lived with 3 other students in an apartment, and since I was interested in languages, one of my roommates who loved everything Japanese, said he would like to learn Japanese, and started with Pimsleur I-III. He quickly got bored, but I used the opportunity to download to my ipod all the lessons, and I bought a Colloquial Japanese book (I went through this twice since then, and listened to hundreds of hours of Japanese101 podcasts while out and about, walking my dog, also doing LingQ and other internet resources, watching Japanese shows and looking up words and expressions). Since the opportunity happened to present itself with the Pimsleur course, I took it and dove in, not thinking logically about how this will eat into my time for Mandarin. There is such a community of people learning Japanese, and so many outlets online, media, meetups, all focused on Japanese, that it was easier to get caught up in the excitement of Japanese than Mandarin. My girlfriend (now wife), also mentioned that she would be interested in visiting Japan some day, but less interested to go to China... Ok, good enough reason for me to dive into Japanese. After having studied (again I have been busy, so I haven't been able to obsessively study, but consistently) for 2 years I booked a trip and spent a little over a week in Japan in Spring of 2017, and was surprised to find that my basic Japanese was useful and able to get me through simple conversations and situations at the train stations, hotels, and restaurants. Japanese workers and people I met were often thrilled with even my basic Japanese, and didn't just switch to English on me. The culture just drew me in. I love the levels of formality, the ceremoniousness of the culture, the pride in their work, the artistry even in simple, every day things. Not to say I don't also see some negative aspects. Like all cultures, it has it's advantages and disadvantages, but I was taken in by it all. When I came back to the USA I was further motivated, and found it easy to find recommendations for more Japanese media, readily available shows with English subtitles (still not good enough to understand without subtitles), movies, music (even though I still haven't really gotten into the music). I've developed a love for Japanese food, and this constant thinking about Japanese and enjoying the culture, watching shows, going to Japanese restaurants, etc is a stronger motivator for me than my practical pressure to learn Mandarin, so it's easier for me to spend almost twice as much time on Japanese as I do on Mandarin, and so my Japanese has caught up, and I believe it has surpassed my abilities in Mandarin, even though there is no 'practical' use for the language here in NY. I just enjoy it more (for now... hopefully someday I'll go to China, have a similar experience, find Chinese media that I enjoy etc, it just hasn't happened yet for me).
I don't regret studying Chinese, I also don't regret that my level is still just advanced beginner-lower intermediate in both despite years 'studying' both languages. If you would rather dive into one, and don't want to end up like me, my suggestion is to follow the one that you think you will be more culturally invested in, and ignore any other reason, because that will be the stronger motivator long term for study than any practical reasons.
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