Cascading conventional filter with matched filter
No, it is not “always” better. 

One would  prefilter in circumstances where it makes sense, like Eckart filtering where the signal is random and the background has a known fixed component.

Filtering, generally introduces correlation in a time series.  A simple matched filter is derived under the assumption of a white background noise. If the prefilter is a whitening filter, it is better but each situation requires its own analysis.

Food for thought, if both filters are LTI, a prefilter can be a post filter.