I'll take a quick stab at your question about why Ron Paul and not Bob Barr or Chuck Baldwin -- individuals whose names will actually appear on the ballot. I think Ron Paul distinguishes himself from all other candidates on several important pressing issues on my mind: the US economy, the US dollar and runaway creation of debt and other US government obligations. Ron Paul is the only candidate that I am aware of advocating for the elimination of the federal reserve, eliminating our fiat currency and bringing back the US dollar tied to gold, silver or something else of some value other than IOU's. I would urge you to look at Ron Paul's positon on those issues and, if you are at all concerned about the US economy and how we will pay for the 98 trillion dollars of obligations we owe, you will see why I am a supporter of Ron Paul and the elimination of the federal reserve and fiat currencies. Otherwise, I see hyperinflation being the only other option (which seems to be where we are now headed) available to the US to pay for those obligations with worthless dollars, at a price that punishes retirees and those that are savers and have learned to live within their means. The federal reserve (a private corporation of regional bank representatives) should not have the authority to expand or contract the availablity of US dollars without Congress' prior consent or approval. To allow this to continue allows the bankers to manipulate credit/debt beyond that which is prudent, never mind constitutional. Again, I would urge you to read Ron Paul's book, The Revolution. It will not take you long to read it and it will clearly detail the differences you are seeking among the other candidates.
As to your implied issue that the other candidates like Barr and Baldwin are actually on the ballot and therefore stand a better chance to be elected, I am not looking to cast my vote for the candidate more likely to win, but rather, for the candidate that can extricate the US from its inevitable economic collapse that I foresee sooner rather than later. I know of no debtor country with fiat currency that has not seen their currency ultimately collapse and I suspect the US will be no different. When will this happen is anyone's guess, but I am certain it will happen. Finally, by voting for Ron Paul, the message being sent to Washington is that more and more people are supporting Ron Paul and his ideas on these issues which, hopefully, gets more and more people willing to listen to what he has to say and, hopefully, adopt some of his positions as necessary action for us to take.
All this may sound like lunacy, but take a good look at the taxes you pay, the health of social security, our real estate, banking, auto, manufacturing, health care and other US economic industries and then look at our mounting massive debt and tell me if there are any other candidates that are even acknowledging these issues as pressing ones, never mind have an actual plan to address the real causes of our pending economic collapse and not the symptoms.