I too find middle 2 tweaky and horrible. I did a bit of testing on pockets recently after doing a block of fingerboarding involving front 3 drag and back 3, and found that I had made decent gains on middle 2 through this training.
with gains only explicable in terms of recruitment
I always thought middle two are supposed to be the strongest. They are the most useful two even if not.
Doing a bit of observing and asking around other climbers about their favourite pocket position, I came to the conclusion that relative digit lengths play a certain role in this:E.g. the shorter the ring relative to the middle finger is, the more load the ring gets in a mid2 position and the more tweaky this may feel, if not adapted specifically. Which seems to be my case. Whereas the index seems to cope better with the length difference, which is why front2 seems to be favoured by those with bigger digit length differenes, despite being anatomically less favourable in terms of strength than mid2 (shared muscle belly etc.).