Each type of filter design has its strengths and weaknesses, so here is a brief overview:
Cavity filters are typically higher Q, higher power, narrower band (per section) and higher cost.  They are preferred for duplex applications where high isolation is required between bands with close proximity.  The BK-31N is a typical cavity filter.
Stripline filters are typically lower Q, broader band and lower cost.  They are typically preferred for most diplex applications.  The BK-20 series from Microlab is an example of a diplexer that combines or separates the cellular bands between 700 and 960 MHz with those between 1710 and 2170 MHz.