Berdych's upside is much better, though. Ferrer trounces him in terms of consistency, but it's like comparing a consistent 10 to a high-low ace. The latter reaching the top five is considerable, even if it's only for a short while.
ferrer has had the better career
more titles, more finals, higher ranked, better grand slam performance (1 final does not beat several more semis and quarters)
ferrer might not deliver against federer or nadal (on clay), but he beats everyone else. berdych loses to everyone and anyone
berdych deserves credit for treating every match against federer as a slam final
that's about it