I will be flying from Japan to Europe and will need to make an interline transfer (from JAL to a European airline) to get to a city that does not have nonstop flights from Japan. My question is, which airports are the best and worst for connections, and why? My main choices are LHR, CDG, and FRA. I could also use AMS and Rome, but JAL does not have its new flat business class seats on flights from those cities, so I want to stick to LHR, CDG, or FRA.

My number one concern is hassle. I would like to avoid airports that have long lines, frequent delays, or are very difficult to navigate. I don't care so much about things like shopping, lounges, etc. I also hate bus gates (which I understand CDG has a lot of) but can tolerate them if necessary.

Thanks for any replies!!