The Hubble Space Telescope's prime mission, was to determine...

However, the WMAP value was not determined
directly from the data, but rather by comparison
against theoretical models and picking the
model with the parameters which gave the
best fit. This strikes me as kind of "cheating,"
in the sense that all models are by necessity
a simplification, and there are underlying
assumptions which may or may not be valid.

The Hubble value, OTOH, is derived from
Cepheid variables so constitutes a direct
measurement. They only assumption being
made is that the calibration scale for Cepheids
being used is correct.