X10 Conundrum

This image outlines my current head-scratching. (If you don't find other people's head-scratching interesting, turn away now :-))

In green, is my current camera. The XZ-1.
In yellow, is a camera that really has my eye. The X10.

Behind the X10, in purple, is the new Panasonic GX1, with the 14-42 (28-84 Eq) X zoom.

If I'm going to carry a camera the size of the X10/GX1, looking forward, wouldn't the GX1 be the more sensible step up from the XZ-1? Does the XZ-1 already cover enough ground of the X10, in a smaller package? Aside from the obvious viewfinder, what would I gain from upgrading to the X10?

Confused (but still shooting anyway).