If you could only do one size pinch block, what would it be?

Given that isometric training is somewhat joint angle specific, ideally one would use pinch blocks of varying size.
But if time prohibits, which size gives the most carry-over and is most climbing specific?

I'm guessing 3 1/2 inches (ie 2 two by fours) but fwiw, I actually prefer 4 3/4 inch (3 two by fours.)
The wider grip feels more like I'm on my fingertips, rather than having my fingers flat, which is how it feels on the narrower grip.

I’ve been wondering this too. One thing that’s occurred to me is that when the grip gets wide your finger joints at the hand are past 180° which I suspect puts more pressure on the joint for a given weight. Since I already have concerns about arthritis in my index finger joint there I prefer to minimize impact.

Interestingly I just dropped from about a 2.25” grip to 1.5” grip and noticed that I was able to increment my weight faster, though that’s just a preliminary observation. I will likely play with bouncing around in the 1.5-3” range as my performance plateaus and see what that does. My conjecture being that changing from one to another every couple of months will allow more rapid overall gains.

I think the medium range  is where most people are the strongest, going both too wide and too narrow takes you into weaker territory.
When it comes to Trango hangboard, the medium pick is the easiest for me, followed by the wide pinch, and he narrow pinch is the hardest.

But I never need to use these narrow pinches in my climbing because there are no narrow tufa curtains around here. But the wide pinch I have to use a lot. So for me it makes sense to train the wide pinch, not the medium.  

If you can’t think of which pinch comes up most often in your climbing, I’d go for the medium, I think. 

Wanting to up my bouldering level, I've tried to focus on wider pinches recently.  Watching good boulderers it seems like (compared to  me) they deploy thumb catches way more often and really squeeze the crap out of them. I think wide pinch blocks translate ok'ish to a variety of thumb catches.

A little off topic, it seems like strong boulderes do the same thing with their feet. It's like the better you get at bouldering the less your feet support body weight and the more you try to either rip apart of crush the stone.