If you are working with large amounts of filtering and have to invoke invalidateFilter() repeatedly, using reset() may be more efficient, depending on the implementation of your model. However, reset() returns the proxy model to its original state, losing selection information, and will cause the proxy model to be repopulated.
reset() is depricated since 5.0
invalidateFilter() does nothing. -> is used from QML
setFilterFixedString("") is a workaround... but is it the common solution?