Their would be no speed difference. Most IDE DVD-RW drives run at ATA66 speeds anyways. DVD's are too slow to take advantage of SATA, period.
However, their are 3 advantages.
1: SATA is new standard, their are IDE free motherboards.
2: SATA is becoming cheaper than IDE (Believe it already is, but due to volumes of IDE optical drives out their, we've yet to see SATA be cheaper than IDE)
3: SATA has better airflow.