Therefore, why would I, a buyer use this vs a credit card?
Firstly, you just cannot use your credit card (or Paypal, or Western Union) to do certain transactions: sending any amount of money to a family member overseas (WU does not operate in many countries, and has limits), making a donation to an organization censored/oppressed by governments (PP blocks donations to Wikileaks), etc.
Secondly, even when you can use the traditional banking system, it is inconvenient: driving 30min to a WU office to receive money, waiting days for wire transfers to complete, etc.
Thirdly, your credit card is tied to an account that your government, bank, or a court can seize for whatever reason (your spouse making fraudulent claims during a divorce going badly, etc). Bitcoin protects you from that. With Bitcoin, you own a purchasing power that no one can regulate or block.
Fourthly, Bitcoin transactions fees are voluntary, hence very low: typically less than 0.01%. This benefits not only sellers, but also buyers. Credit card transactions cost 1-2% (even if you do not see them as a buyer, the seller increase its prices to cover them).
Fifthly, the USD in your account tied to a credit card depreciates over time, because the Federal Reserve prints money continuously (causing long-term inflation). Whereas with Bitcoin your purchasing power is preserved or increased over time, as the maximum number of Bitcoins is capped (causing long-term deflation). Therefore you do not have to resort to various more or less risky investment options to preserve your net worth over your lifetime.