Capacity or caliber, what is more important in a carry weapon
I excluded revolvers because of their limited capacity.
Sounds like you've already selected the criteria which matters most to you ...
I started my LE career carrying an issued 6-shot revolver and a 7+1 Colt Commander for off-duty.
As time passed I was issued different 'high capacity' 9mm's & .40 S&W's.
I finished my career carrying an issued 7+1 .45 compact on-duty and a 5-shot J-frame off-duty most of the time. My, how times change ...
Now that I'm retired I choose my CCW weapons for their ability to work well with my activities and personal desires.
Capacity is rather low on the priority scale. Matter of fact, so is caliber. Something in one of the more commonly encountered service/defensive type calibers, and no less than 5 rounds (because I like the J-frame).
I tend to look for functional reliability, durability under reasonable conditions, inherent accuracy and the ability to serve whatever perceived needs I anticipate.
A 5-shot J-frame serves me well most of the time, although I have a number of pistols chambered in 9mm, .40 S&W and .45 ACP from which to choose, as well. The magazine capacities of them run to 6, 7, 8, 9, 10 & 12 rounds.
As you can tell, neither capacity nor caliber worry me overly much.
What
does concern me, however, is maintaining my abilities, skillset and mindset to effectively utilize whatever I may be carrying at any given time ...
The skills and mindset are more important to me than the specific tool, when it comes right down to it.
While I don't have any personal stake (or interest) in why someone chooses to lawfully carry a handgun as a defensive weapon, I would suspect that overly focusing on either caliber or capacity might sometimes serve as a distraction from giving due consideration to the more important, even critical, priorities ... such as knowledge of the applicable laws, familiarization with whatever weapon is chosen, developing and maintaining good skills, preparing oneself physically to withstand the rigors of unexpected stress (to the extent reasonable given any individual physical limitations or restrictions), and, developing the mental and emotional conditioning to be able to intentionally and effectively function in a crisis situation.
Caliber & capacity?
Sure.
Pick whatever you like.
I do.
I will acknowledge to having passed by carrying the CS45 (6-rd mag/.45 ACP) in favor of a 3913 (8-rd mag/9mm), upon occasion, but then at other times I decide just the opposite.
I do shoot a fair amount to maintain my skills, though, regardless of whatever I choose to carry.