Mastering

I've read that the SACD format uses a 1-bit word length throughout. Why is this the case, and how does it yield higher audio quality than standard 16-bit CDs?

I had four tracks transferred to vinyl and told the pressing plant to do any necessary EQ'ing required. I got the test pressings back and found them to be very harsh in the upper frequencies when compared to my CD master. Should I get my tracks professionally mastered for vinyl next time?