Well okay, then ... didn't mean to butt in or denigrate. I've done both (10+ or less than 10), so I thought I might have a seat at the table.
The obvious advantage to having more rounds is being able to shoot more between having to load.
Whether that's a
practical advantage is going to be situationally dependent and shooter dependent. Take your pick and hope for the best outcome.
Folks who spent so many years carrying 5/6 shot revolvers, or single stack pistols with 7-9 round magazines, may not be quite so fixated or adamant on how much of a priority or advantage having hi-cap magazines may be. (Yes, even back when the most common double stack pistols were Hi-Powers & M59's, it was typical to here them referred to as "hi-caps" because they held more rounds than revolvers or single stack pistols.
)
While I've talked to cops who have been in shooting incidents who have fired 1 or more of their hi-cap magazines, the significant number of them I've known have fired between 1 and 8 shots during an incident (those are low/high counts, and cover both on & off-duty incidents).
I've listened to a number of other firearms instructors over the years who have reported similar round counts from among their people.
The type of unusual incidents we sometimes hear about where cops (let alone private citizens) have burned through their primary and/or spare magazines are noteworthy more for being infrequent, odd and unusual, than for being the rule of the day.
Now, having a pistol that uses 10-rd magazines gives you 4-5 more rounds than a snub or standard size revolver, and perhaps 2-5 more rounds than some smaller single stack pistols.
Choosing personal handguns for dedicated defensive roles is an equipment choice that's certainly subject to task-oriented considerations, as well as considering the likely risk assessment potential.
If believing that having more than 5-9 rounds is a necessary, or even just a desirable, priority ... then that's an individual's decision.
