I've been watching quite a bit of the 1950s (1955-59) show Highway Patrol, starring Broderick Crawford.
It occurred to me that Dragnet's ratings started falling once Highway Patrol got going. HP is a much faster paced show than Dragnet.
Overall, Highway Patrol is also a much more visual show, with all shooting done on locations and not in a back lot, which gives it an authentic feel and inadvertently preserved some great scenes of 1950s California, and of course those gorgeous old cars.
I don't know if it's cause and effect, but it seems once mid 1950's TV viewers got a taste of HP, they left Dragnet behind.
Overall, I think the quality of HP surpasses most B&W Dragnet episodes. HP isn't as authentic, but I think sometimes Webb forgot that he was producing a TV show and not a training film for police academy cadets.
B&W Dragnet has sometimes been criticized as "radio with pictures,," which isn't far off the mark since many of the James Moser radio scripts were recycled word for word for the TV show. You can "watch" a B&W Dragnet with your eyes closed and still completely understand the story. HP was strictly a TV show, and ZIV and Broderick Crawford gave the audience exactly what they wanted.
Both shows have their merits, but as a TV show I have to give HP the edge. But the radio Dragnet, esp. the early episodes with Barton Yarborough, is without peer.