Stop being dumb. Ripple doesn't enable instant payment either. Whatever your send via Ripple is useless until the recipient gets what he really wants.
If a vendor wants to receive 10 BTC for his product/service, getting an instant IOU in Ripple is pointless. He will still need to wait for 10 to 30 mins for that BTC from Ripple to come into his real wallet.
If a vendor wants to receive $10,000 for his product/service, and he is located in a small town in China, getting an instant IOU in Ripple is pointless. He will still need to wait for whatever amount of time needed for the money to be wired into his bank account.
Need to withdraw diminishes as the network expands; the IOU becomes a functional placeholder for the currency. Depending on the currency, withdrawal from the gateway could be rapid---and potentially instant if banks begin to act as gateway services.
XRP itself can also be used, eliminating need to deal in IOU.
Both IOU and XRP beat BTC in speed, no contest.
Bitcoin itself is great, and Ripple supports Bitcoin for faster payment transactions.
Ripple is a promising alternative to the closed centralized payment systems that are overtaking the landscape; they are able to thrive based on the limitations of Bitcoin.