I have three CCW guns I rotate among, depending on the occasion: Russian Makarov, 10-shot capacity, 9-mm Mak loaded with Speer Gold Dots; S&W Model 642 Airweight Hammerless, 5-shot .38-spl, Crimson Trace Laser Grips, 158-gr JHP; Herters double-derringer in .357-Mag, loaded with .38-Spl 158-gr JHP.
From my personal experience in protection from physical assaults/robberies, here are some factors to consider:
(1.) If you have to use your gun, fast, easy access is far more important than having an impressive gun. Ankle holsters are generally inconvenient, unless you can fake an illness.
(2.) Engagement will be at very close range...likely about 5-feet or less.
(3.) As soon as the "perp(s)" realize you are armed, they generally skedaddle VERY rapidly. In the three times my guns saved me (once from 4 young toughs!), I never had to fire a shot.
(4.) One shot fired by anyone attracts attention and the police. Good for the victim, bad for the "perp"...so they don't want shots fired.
(5.) Considering all of the above, you are rather unlikely to get into a pitched gun battle requiring large cap mags and reloads.
Comments on my three alternative guns: The derringer gets the most use...smallest, lightest, easiest to conceal. Next comes the S&W Airweight...the laser is useless in daytime, invaluable in dim light and night. Where the bright red dot is, is where the bullet will hit...further aiming or gun positioning unnecessary. I rarely use the Mak...although slimmer than the Smith, it's the heaviest and I don't need the ten round capacity.
Hope this spurs your thought process!