You aren't just picking a language, but also a school, so consider that too.
as well as which is easier for you to attend. You have to be committed to the language immersion programs through at least 4th or 5th grade to get the benefit. Also, which country do you want to visit? Because you could end up, sometime in your life, going there with your child. We chose Chinese, and have loved it. One thing to know, though, is that learning Chinese is hard because you have to learn not only the different tones, not only the romanized pinyin, but also the characters, which don't really follow a rhyme or reason, and just have to be memorized. And you have to learn how to write the characters correctly. It ends up that learning Chinese will be a bit more homework, and their fluency will be less than the other languages. All that being said, we have loved doing Chinese immersion, our kids speak it well enough to navigate trips to China, and we love the Chinese people and much things about their culture. It's been fun.
One other thing ... the most important thing about dual language immersion is the learning of another language and what it does to your brain development and cultural awareness. I think that's the biggest benefit. So which language you pick is secondary. If there's a school you like that is close by, don't feel badly about doing that language.