Comparing Transatlantic Voyages

We’ve done four Transatlantic cruises, but three have been Eastbound, from Florida to Spain (Miami or Port Canaveral to Barcelona.) I overlaid the maps from the three Eastbound cruises on one map, and you can see how similar the routes are. A Captain can sail however he would like but the reality is that the routes are almost as fixed as the Interstates, since they are based on currents and sailing the Great Circle (I presume.)
So, this is 2014 (Miami to Barcelona via Funchal, Madeira), 2015 (Miami to Barcelona via Funchal) and 2017 (Port Canaveral to Barcelona via Bermuda, Funchal and Malaga.)