Obviously, these factors are yours to weigh (rather than ours to 'vote' on), given they have financial impact on you.
Seems to me you are w-a-y better off financially to do ED in January. The potential
downside of this choice - not a certain one - from my reading of the ED Wiki is bad weather and consequent loss of insurance coverage. So...you have two options re: managing insurance coverage: 1) deliver the car straight to a drop-off center for shipping home, and use a rental for whatever sightseeing you want to do, or 2) if wx conditions are poor at times after taking delivery, park the car for those periods and use the extensive public transport wherever you happen to be while the roads are dicey. This latter option only requires you to have a flexible itinerary.
Given the weather in the area adjacent to Munich, you could make your choice between 1) and 2) based on the weather you are given at the time of your arrival. (See the BBC's description of the Central & Southern Hills region of Germany to understand why. http://www.bbc.co.uk/weather/world/c...ml?tt=TT003650
). And finally, you can shape your itinerary to minimize weather problems by grabbing a weather window to move the car to a warmer climate, if it's important to see some of Europe while driving your car.
As for your (premature) decision to committ FF miles, the cost of rescheduling their use, as you describe it, is far less than the much larger expense you describe if getting the car in the Fall.