[newbie] Are all RPMS created equal?

[The Conways]

I remember reading somewhere that it is better to compile source code than
use downloaded RPM's because the Red Hat file system hierarchy is different
than the one used in LM, just as other distributions have different file
systems.  Is that also the experience of everyone on this list?  Or is there
an easy way to get around this problem?  Or should you only use the cooker
RPM's coming from LM?