I’ll take a stab at a few of these complicated issues.  1st off this isn’t an “either/or” question.  Many factors figure into each decision.  Price is usually most important.  Time is second.  You need to figure the full time/cost in making any comparisons.  For example, airfare + taxes + cost to get to and from the two airports = cost of train ticket (or a day of the railpass + reservation).  45 minutes to get to airport + 2 hour check-in time + 1 hour flight + 1 hour to get out of the airport and into town as compared to 5 hour train trip.  Always figured in my personal decision is the fact that I hate the hassel of air travel and that it’s much easier to change plans if you don’t have to deal with a scheduled flight. 

  You will probably find that flying out of Budapest on a major overseas carrier is very expensive.  Train to a major hub in Western Europe will take lots of time.  Look for a budget flight to a major city, or taking the train to Vienna if you can find a decent flight home out of there.

  Try www.railsaver.com to see which, if any, railpass is the best deal.  Follow the “I have a good idea of my itinerary” route and click “I prefer using railpasses (to point to point tickets) ‘only when it saves money.’”  It usually recommends a combination of railpass and point to point tickets.  I think a 3 country select pass for 5 to 8  days in France, Germany, & Benelux with cheap flights to and from Morocco and point to point train tickets will probably be best.

Just reiterating what oldlady said about flying from Budapest.

I flew home from Budapest on my most recent Eurotrip in August.  It wasn’t as expensive as I was expecting, but you should definitley be able to save some money by taking the train to Vienna (which is only around 3 hours).  I ended up connecting in Frankfurt for my flight home, since there are very few non-stop flights from Hungary to N. America.

This might also mean that it’s cheapest to put Budapest in the middle of your trip. For example, fly from Paris to Budapest on a budget flight, take the train from Budapest to your next city, and arrange the rest of your itinerary to end in a city with a cheap flight back home.
 
If you purchase cheap flights (or cheap rail tickets, because these are often available on special also) months in advance, it does limit your flexibility. So far, I haven’t minded this, particularly since all my trips have been 2.5 weeks or less.
 
What is your home airport city?

Train from Madrid to Algeciras (ferry to Tangier) will take about 5h30m. The price without discount is about 60 euro. (www.renfe.es)
The ferry from Algeciras to Tangier will cost around 33 euro for a single trip. It takes about 1 hour. (http://www.balearia.net/eng/index_balearia.htm)
The train from Tangier to Casablanca will take about 5h45 and cost 175 dirham for a single trip (http://www.oncf.ma)
 
Although it’s probably an adventure to go over land, I think I would take the plane. Inland Spain during summer isn’t interesting at all, it’s mainly dried out. I don’t know about Morocco. Plus this trip is gonna take you a very long time.
 
I would take the EasyJet flight from Madrid to Casablanca for 26,99 euro (prices at the moment at the beginning of May) (http://www.easyjet.com)
From Casablanca I’d take the Jet4You flight to Paris Orly for 79 euro (http://www.jet4you.com)
 
About you 2nd question, where do you fly from/to in the US? I guess you can get better deals from other main hubs like Paris, London, Frankfurt or Amsterdam. There are many low cost carriers flying from Budapest to or close to the different hubs. Also a train to Vienna is only a few hours.