Technically, I believe DVD-A is better because as a medium, it can store so much more information than a Super Audio CD - but that is only a theoretical answer.
Of course, the final product would depend upon a number of variables such as master and transfer quality - so it may also be possible - to have a SA-CD which pushes the limits of the media to the max - while (also theoretically) a "lazy" DVD-A does no more than preserve an LP in it's original state - scratches and all! (I know it is an extreme example - but it's only an example guys - not doctrine!).
I guess therefore it depends on the title, but, all things being equal DVD-A should be better.
"Listen to them. Children of the night. What music they make."