Will disembark a river cruise early Sunday morning in Basel. Planning my return flite to USA, am I better off taking a cab from wherever the boat docks to Basel airport (how long a ride?Fare?) or take the motor coach provided by the cruise line, & drive to Zurich airport?
Depends where you can get a direct flight from. I see you are from Chicago. The only transcontinental flights from Basel are to Montreal. Swiss flies to Chicago O'Hare from Zürich, Lufthansa and United Airlines fly there from Frankfurt.
So fly home from Zürich.
Getting to Zürich airport is easy from Basel station, 1h20 by train. But, if you are getting a free bus direct from your boat that may be easier. No way drive a hire car.
A taxi from the boat docks to Basel airport costs ~CHF 60 and takes 10-15 minutes. to Basel SBB stations somewhat cheaper and quicker.
see my advice in this https://community.ricksteves.com/travel-forum/transportation/san-francisco-to-basel-airlines-and-connections (obviously it's teh other way around).
If the ZRH flights are good and the free coach is a reasonable connection then go for it.
If the flights are good but the coach would leave you hanging around for hours at the airport try the connecting train offer.
If ZRH flights are not good, try the FRA option
We took a river cruise a few years ago that ended in Basel. We took the transfer to the airport offered by the cruise line. It was so easy. On to a bus and then dropped off at Zurich airport. I don't think the drive was very long, under an hour.
Can I assume that this cruise starts in Amsterdam, so you would be flying from ORD to AMS to start?
United/Swiss have nonstop flights into AMS and out of ZRH, and right now, they are looking pretty cheap ($800).
There is another option: shared van to Basel train station, and train to Zurich.
We were on a Viking Rhine cruise from Amsterdam to Basel this June, traveling independently (e.g. no cruise line transfers / airfare included). The Viking front desk asked us to check with them about departure arrangements, a few days prior to disembarkation. We were docking at Dreilandereck, a good distance from Basel city center. The front desk was able to set up a van to Basel train station for 56 euros, shared with two other couples, so each couple ended up paying €20. The price was great, and it was a convenience to pay in euros, since we hadn't had a chance to get Swiss francs yet.
If you dock closer to city center, a tram to the train station would be another option.
We went to Wengen and Luzern for a few days after Basel, but you could just as easily go straight to Zurich on your disembarkation day. Either way, the cruise ship front desk was very helpful to us in arranging transportation. I would research your options, then check with them prior to disembarkation.
Hope this helps!