The z and the xs aren't really comparable. The Z has a huge platform for riding on if you miss a clip in. If you want that get the z(if you want to ride in soft shoes pedal strike be damned get some of the older simanos instead though.)

The only real comparison can be made between the clipping mechanism. The Z uses the older style like the aliums while the xs/xe use a newer one. the newer one is a lot crisper and easier to get into and out of imo.

I know nothing about those shoes If they are from performance just get them and then return them if you end up not liking them.