Your decision should be based on how either option (and others) fits your long term future plans. Not only what will you be earning, but what will you be learning? The advantage of working at a place like McDonald’s is that you will be interacting with people – customers, management and fellow employees, in a real business setting, but you will not learn new IT skills. Bidding online for development projects may improve your technology skills, but is a pretty anonymous workplace. Ideally, you should look for something that offers both. For example, if you are of legal working age, there may be an opportunity to work for a local end user company or systems integrator supporting open source rollouts, in which case you get a more rounded experience.
If you are looking for an impartial source on <a href=”http://www.odesk.com/trends”>developer trends</a>, and/or opportunities to try your hand at freelancing, consider visiting odesk.