Connecting TGVs is hard, but I’ve done it before from Lausanne to Nantes, through different train stations in Paris no less. Was worth it, since I would have needed a 30-40 minute train trip to Geneva anyways.

Airports are usually outside of the city, train stations are usually inside the city, that is a big deal worth a couple of hours. Geneva airport is a bit more convenient, but if you are coming from Lausanne, it’s still an hour.