Hi there! I have never studied in either countries, but I have thought about doing my MA and PhD in Germany so I did a lot of searching. I am speaking from the info I know, and I hope they help you a bit!
Language: If you are doing quant stuff it's more likely you are using English exclusively in academia. Some survey projects aimed to German speaking audiences might require German skills, but in general, you should be fine. Also European countries have pretty close academic relationships with each other, so most European scholars speak good English just to better communicate. As for daily speaking, major cities or college town like Berlin and Heidelberg have a very considerable English speaking population, but in rural places ppl (especially elders) generally only speak German. Just like any other non-English-speaking places. From my own experiences traveling in Germany, they usually speak good English. And it is never hurtful to learn a new language, right? If my memory serves, German government fund programs to teach immigrants and foreigners for free.
Money: Living in Germany is cheap. Like, really cheap. Eastern part of Germany is cheaper than western part. If you are not sure you can check the cost of living online. Plus universities don't charge tuition, give you cheap/free transportation card, and you rarely need a car. But if you do own a car (although I don't see why that's necessary), the gas is very expensive. It's expensive across Europe.
Academic tradition: most German schools provide solid training and they treat their research seriously. Also, they bring up questions and topics that are not common in the US, which is a nice way to think about stuff from a different angle. If your area of research is not the more popular in the US, Germany could be a nice place to look at. That said, many schools are not very competitive in the US, because they are in different systems and American Sociology value North American schools more. So if you are moving back to US, it is something to keep in mind. There are famous institutions considered reputable in US, depends on what your field of study is. I think the best way would be to ask your academic advisors and other uni profs, since they are experts and are more likely to know what's going on in Europe. Within Europe/Germany, most unis have solid reputation.
Another note on German academia: Besides Universities, there are other reputable (if not more reputable) research institutions across Germany. Institutions like Max-Planck and Leibniz have many research centers (NOT limited in hard science) all over the country, and they are worth to look at. They pay well, have a lot of research funding, and are usually internationally reputable.