Which tax policy is more fair?

There is one part of the highly contentious tax issue that I don’t feel has been directly addressed, so I am asking it as a separate question, and I am asking it in the “General” section as I want to stay on this part of it as opposed to taxes in general.

Some people claim that raising taxes on the rich is unfair since they (or their parents, or grandparents…) earned that money through hard work and should get to keep as much of it as possible. This group complains that a small segment of the population pays nearly half of the income tax. (The exact numbers vary by time and the speaker, but the top 10% paying ~40% of the taxes is close to the numbers I have seen most often and a good enough approximation for this discussion.)

Others feel that the rich are getting a free ride at the expense of everyone else and thus the top tax rates need to increase.

My own thoughts are that the top 10% earn 50% of the income while (as of 2009) 47% earned too little to pay taxes at all and earned only ~15% of all income. That leaves the 43% of people who earn ~35% on the income to pay around 60% of the taxes, and I feel that that is not fair.

So which is more fair; letting the rich keep more of their hard-earned money at the expense of others, or letting everyone keep what they earn?