are FC4 source RPMS for x86_64 and i386 different?

[D. Hugh Redelmeier]

There are separate downloads for source RPMs for x86_64 and i386.

As far as I could tell, the FC3 updates SRPMs were identical for the two 
architectures.  This seems like a good thing, if it works.

I use both architectures and would like the SRPMs, but hate wasting
bandwidth and disk space.

Are there important differences between the two packages of SRPMs?
Should I download both?

Should only one set of SRPMs be released?  Perhaps with a small number
of arch-specific SRPMS for those that don't work on all archs.