In my experience, there are far more runners advancing by the ball getting past the catcher (whether it be technically a PB or WP) than by stolen base.
Also, at least half or more of the runners advancing by steal do so on the pitcher. Some percentage also steal on a pitch that goes in the dirt and has to be blocked rather than caught by the catcher, which, even if routine, the catcher can't make a throw in time if he does his job correctly.
This all means, in my view, this question isn't even close. Give me the guy who can keep the ball from going to the backstop.
When analyzing why teams win and lose in HS years and prior, I think blocking ability is the single most underrated factor.
I've witnessed many HS games where several bases were given up by the catcher's lack of blocking ability. Then the catcher throws someone out stealing and everyone goes gaga.
My kid catches. He knows his task is to prevent any pitch from hitting the backstop. Doesn't matter if runners are on or not. The next (related) goal is to minimize how many bases were advanced during the game on pitches that were not hit.
In HS ball, he's trying to block (rather than catch) about 20% of the pitches. (He plays JV at this point. Varsity pitchers probably reduce this by half or so.)
That means in the course of a game he is trying to block 25 - 30 pitches. Some of these are 55 foot fastballs. These are very hard to block because they come in faster, bounce lower, and the catchers aren't expecting to have to block them.
Most balls requiring blocking, of course, are curves.
If my kid block them all, then he's had a great game.
If a couple of pitches get past him, it is average. Sometimes he blocks one but it gets far enough away from him that the runner advances.
The exception is a straight steal off a pitch that can be reasonably caught and thrown, where the pitcher both kept the runner close and had a pitching move that gave the catcher enough time to have a chance at throwing the runner out.
My kid gets maybe one legitimate chance to throw a guy out maybe once every two games.
All this is to say that if you ask what is more important- a good block/receiver or a strong arm? It isn't even close.
Give me the kid who keeps the ball off he backstop. At least in the HS years.