CSA are scrapping the JFK route at the end of the summer timetable.

If you are flying from JFK (or MIA- though I am not sure exactly when they start flying there), I would fly UX- the business cabin on their A330 is very nice, you don't run the risk of a middle seat a la AF B777 (and others?), the lieflats are good enough for me, service strikes the right balance between friendly and professional, and it's easy to connect at MAD...Plus the route is newish, therefore you have more chances of an empty seat next to you.

Flying from elsewhere, your choices will normally be restricted to AF/KL/DL. If you're starting from a place without direct service to the European hubs and need to make two connections, I would consider XXX-JFK-LYS-PRG for the ease of connecting at Satolas.