After just riding 400 miles in 3 days on my BI-CYCLE with a 40lb load in panniers — I am going to argue that the HUMAN powered bike, while not quite as fast, doesn't require gasoline and I have gone on more than one multi-day trip like this without a single mechanical incident.
It is amazing when you can cross multiple STATES on a bicycle and sit back knowing YOU DID THAT. Granted, not everyone is going to find that enjoyable.
If I had mounted the FRONT panniers, along with the handlebar bag and under-seat bags I have, I am quite certain I can load up my touring bike's capacity to well over 100lbs — I just would not want to RIDE a 100lb bicycle. Just having to carry a 60lb bicycle up a flight of stairs wearing cycling shoes after it rained and they were slippery was not fun (but a motorcycle would be even less fun).
Bicycles are more or less SILENT too. I need to keep a bell on my handlebars just to warn people I am coming so they get out of my way as I am riding along, or else they won't hear me until I am 3 feet away.
Not saying motorcycles are not worthwhile, just another thing to consider! You get a lot of the same advantages, with some disadvantages, along with a few advantages that the motorcycle doesn't give you!
In a ZOMBIE situation — I would prefer to have a MOTORcycle.