The Silca will pump up to a higher PSI than the zefal (at least thats
what I remember).
Be careful with the Silca, they are known to blow the back end off
the pump (they arc really well across a road if aimed right!) the thing
to do is to not let go of the back end of the pump so it doesn't shoot
off.
There was some detailed info about why this occurs on CR list about a year
ago, I'll see if I can dig it out of the archives and repost it here.

Marty