Doug38PR; While I certainly agree that the S&W M&P and Colt O.P. were the "major" police revolvers of the 20th Century,more than a few departments prefered the S&W Regulation Polices and Colt Police Positives(both "regular" and the P.P. Specials,usually in .38 Special). It amazes me,but many departments,felt adequately armed with the .38 S&W or .32 S&W long round right up through 1950,or so! In fact,"police cartridges" were made in both of these calibers,up through the World War Two era. A cartridge collector,I know,has some "metal piercing" .32 S&W Longs(or Colt N.Polices). Might pierce some of the "steel challenged" autos built now,but not the old heavy gauge steel/wood of a bygone era!
The Police Positive(and Special) outsold the S&W Regulation Police,because it was;a) made in .38 Special b)held 6 shots to the .38 S&W R. Police only holding 5(both makes held 6 in the .32 versions.
Many urban departments had foot beat cops,not many squad cars,and the extra 10-12 oz.of the M&P and O.P. probably added up walking many miles a shift,so they liked the smaller Colts and S&Ws(plus they were cheaper on the budget!!!).
I love the Colt E/I size frame,or my hands do. I shoot the best with this size gun,but the largest N frame pre war S&Ws,with the old NON magna grips,feel about the same. I have many of both these styles of gun. For me,the older M&Ps just feel too LIGHT,and while I have 3 pre war M&P Target Models,only the .22 Outdoorsman feels right for me. The 32/30 and .38 Special just feel muzzle light,as does a .38 Special Victory. Yet my 2 post wars,on the "M&P Frame,K size", a .22 Jet and .32 Magnum,are much heavier guns,and don't have this feel.(I also don't like any D Frame Colt with over a 3" bbl.)
No getting around it,the Colt was a heavier gun in all 3 frame sizes(an hour or two on my range with a pre war N frame S&W,makes my Colt New Services feel "too heavy".)
Everybody has a favorite,and you go with what feels best. There are plenty of stories about BOTH makes having problems. While the O.Police could handle heavier loads,how many city P.D.s bought anything but the "standard" 158 gr. RNL?
As far as using it as a club,most older cops I knew,had a very good relationship with their long billy,and in a fight,many prefered to use the lead "sap: they carried in their pocket! Also,how many ever really had to even "draw" their service revolver??
Finally,if you are ever in Auburn,Maine,very near to my town,stop in the local P.D. and ask to see the "testimonial" to an officer who was killed around 1950. On the wall is the frame and barrel of his O.P.-BENT! No not from sriking someone,but this was the point of impact when a fire engine hit him. He saw fire trucks,answering a call,about to converge at a blind intersection and heroically went into the middle of the intersection(he'd been getting traffic clear/stopped) and was struck by one of the engines that could not stop in time, The O.P was in his holster,the point of impact for the Seagrave pumpers front end.
Bud