The Aleph designs should be easier to mate with various speakers due to the lower output impedence, so it's operation will be less affected by the speaker's impedence.
As for sound quality, I have no direct experience with either of these circuits, but I have tinkered with many, many preamp circuits (which are really just mini power amps, only much cheaper and easier to fiddle with). In my experience, the simplest circuits don't always sound as good as more complex designs. I havn't tried anything as simple as the Zen, but I've certainly tried out several circuits very closely resembling the Aleph.
Now, many people on this forum may disagree with me, but I no longer buy into the simplicity argument for sound quality. I believe there is a trade-off between the degredation each extra component adds and the performance improvement it contributes. This includes how a given circuit will affect the performance of whatever it is connected to (source and load), and this is all too often overlooked. Ideally, you want an infinite input impedence and zero output impedence. In my experience, input and output impedences can make an enormous difference in sound quality. As well, there's a lot to be said for gains in efficiency, since the cost of an amp project is so dramatically governed by the amplifier's efficiency.
In any case, my tendancy would be to lean towards the Aleph rather than the Zen/SOZ.