I love sketches of spain. I think it, and the previous collaborations with Gil Evans (Miles Ahead and Porgy and Bess, and I suppose Birth of the Cool, though I wouldn't put that in the same group - not in terms of quality, it's excellent, but rather that it's aiming for something very different musically) are some of the finest work he did. This is partly down to Evan's genius as an orchestrator. I don't think Rodrigo's Concierto de Aranjuez has ever sounded so wonderful.
But have a listen and hear for yourself.
regards, Tam