Again, with correct instruction and correct training engaging targets with a shotgun at mid ranges (out to 100 yards) is not that difficult. Select slug drills can be accomplished very quickly, quicker in most cases than transitioning to a secondary weapon.
Who is going to load slugs into a shotgun for CQB?
I would load a CQB shotgun with slugs!
In fact my CQB shotgun is loaded in part with slugs AND buckshot and has a sidesaddle for extra slugs. A select slug drill enables me to quickly transition to a shot out past 100 yards with a greater degree of confidence and accuracy than a pistol. Remember a new hi-vel slug weighing in at 7/8 .oz will only drop some 3 inches from 50 to 100 yards. As for buckshot research info regarding "Choke Precision Bonded buckshot" with shot cups that enable buckshot to mimic the external ballistics of a slug and the terminal ballistics of buckshot out to 100 yards.
I didn't want to put it as strongly as this, but supposing proficiency in either weapon, a pistol over a shotgun is, relatively, a very poor choice when it comes to CQB.
If the pistol was the BEST for CQB and the only thing that one could maneuver in a house why then do the HR teams choose subguns, carbines, and shotguns, backed up by pistols?
I know from even my limited training and experience with an Armed Offenders unit there was not a man on the squad who would take a pistol over a shoulder fired weapon.
Regards,
HS/LD