I've swallowed, it didn't taste too bad :S what's all this "it tastes horrible"?
I think spitting is gross; girls don't spit everyday, so it may be a bit messy and if I was a guy, and she spat it out, that would be a huge turn off.
And about which is better - oral or sex/penetration? It kinda depends on certain things because everyone is differnet and are turned on or off by different things.