I think the unit scaling needs a bit getting used to, but they are both fine. In the end I think I prefer the pieces zooming since then they are always optimatically visible.
On a sidenote, when you zoom out enough you get the clothmap, right? It seems to me that once the clothmap finally appears, the icons on it are way too small for me to make anything out of it. For perhaps these grain icons and such this is fine because I can tell what they are, but there were some little icons that were rather detailed and very, very small. On the clothmap it became so squiblly that I was not able to tell what I was looking at. This was because once the clothmap kicked in, everything was too small for me to read it.