Both SACD and DVDA provide theoretical and actual audio quality improvement over CD. But not enough better than a well made CD to make it worthwhile for 2-channel. The major benefit of these new media is multichannel, and if you can't or won't try MC don't bother with SACD or DVDA.
Of the two I think that DVDA is best. There are some technical questions about SACD HF performance, although I don't hear a problem. The DVDA protocol is much more flexible as to what the producer wants to use the bandwidth for. For example some discs let you choose your acoustic location in the hall..."Stage" or "Audience". The video on many DVDA is quite interesting...interviews with the performers, historical notes, and such. SACD lacks these extra features.
Of the two I think that DVDA is best. There are some technical questions about SACD HF performance, although I don't hear a problem. The DVDA protocol is much more flexible as to what the producer wants to use the bandwidth for. For example some discs let you choose your acoustic location in the hall..."Stage" or "Audience". The video on many DVDA is quite interesting...interviews with the performers, historical notes, and such. SACD lacks these extra features.