Frankfurt has very good train connections as well. Specifically to Cologne which is via the hi-speed tracks, but also to Amsterdam and Vienna.

One big advantage of Frankfurt is that Germans are much more open to speaking English than the French, and this is an advantage that should not be underestimated. If you don't speak German, but do speak English it's possible to live in Frankfurt. To live in Paris, you have to speak French.

Only Amsterdam (which has English as its official language next to Dutch) is better in that regard. In Amsterdam you don't even have to ask if someone speaks English (that's considered an insult, on the same level of asking someone whether they can read and write).