Very interesting thread, and winter is the time! I have only grown one micro, Red Dwarf. Have grown it twice now, winter and summer, and the summer plant is still with me maybe getting ready to put on some new leaves and fruit again.
The first time I grew it, there were two seedlings and one of them was a "slow poke". I thought it would never amount to anything. But eventually it did grow and actually was larger than my first after it grew into a larger size pot.
One thing I love about the Red Dwarf is the rugose foliage and sturdy growth habit. It never leaned towards the window in my winter grow, just stayed sturdy. And there was no foliage disease until the last of its fruit had ripened. What a huge bonus that is! It seems to have a cycle where, after ripening every fruit, it will withdraw all the goods from its leaves and let them die, then begin afresh with new foliage and buds.
Incidentally, PL leaf curling is a classic response to low light, which I have seen on non-micro tomatoes in house. There are a few varieties that don't seem to do this, but most PL's seem to be prone to it - compared with RL - afaict ime.
I have the wish to try more micros, and I love blacks so excited to read about your growouts.
Just talked to a guy this morning who is going to help me finish the job of renewing my window seals and trim, and when that's done i expect plant fever to take over.... Until then I can't get excited about so much as a microgreen, I am that fed up with insects finding their way into the house for a share of my veggies!
In response to original question, my ideal micro is not leggy or a leaner in dark winter, not prone to foliage disease, and the fruit is never "mushy" or bland. Delicious of course is what we all want
... but in a winter window I would find uses for tomato of decent quality for eating fresh ie not bland and not mushy.
I don't know how the segregation of "mushy" goes, but because it's the thing I hate the most and find most disappointing after months of tending a plant
I cull anything of the kind, on the reasoning that at least some of its offspring would be the same.
But there's no reason why you can't select a plant with "the best" growth habit and a second plant with the best taste, and then backcross them in the next generation to select for super taste with the right growth habit. I think.