I'm sure there are much more experienced people on the island who could help you better as I haven't had experience in taking lots of cuttings from a large mother and having the chance to discern one type of root from another.
I keep my mother plants from seed because it is healthy and ready to keep making more clones. It makes more sense to me to keep the original in the library to make copy's of.
Do you recall, or in your own experience, where the better clones are pulled from? I am considering topping my plants, and I wonder how that would do as a clone, and what type of root system it would have?
If I am remembering correctly, I read this in a thread on overgrow about cloning and I think the person was saying that they didn't want a tap root for their clones. I didn't look into the details or test their theory and I might be remembering incorrectly.
I can share my experience:
I don't pay much attention to what kind of roots my clones are growing but focus more on how fast they get going, how fast they pop out of the small cup and how healthy the cut looks when I make my selections to move them into veg, there are always some that stand out from the rest and the clones that grow roots the fastest usually look the best.
I also have one very vigorous mother that grows faster than all the others and her clones grow just as vigorously.
I have taken cuts from most every place and have had success with them all. IMO The most important variables for quick roots and good clones are cleanliness, humidity and the temperature; (about 75-80 for both). If I am trying to keep a mother, I wont cut a main branch for a clone that is growing from the center stalk at the stalk because it wont grow back, cutting the secondary or third branches that grow off the main branches is the way to take care of a mother. I like to take my cut while the branch is still in its later infancy of growth (while the outside of the branch is not extremely tough or woody yet) the theory is that these younger branches still have the natural hormones in them that will help grow roots quicker. Because of this, I don't believe it is customary to take a clone from the top center stalk, even though it is totally possible.
With that said, I keep my mothers under 12 inches, I will wait until just the right time and get a perfect size cut from the top that hasn't matured past the sweet point for quick roots and also makes a good size bonsai. This top works as a good clone for me a few weeks before those secondary branches are even getting long. The tops usually take a bit longer to take root than normal cuts even at this stage of growth. Keeping the mothers small saves on nutrients, lights and space. I like having vigorous mothers even if I have to trim them more often because I believe the clones from these vigorous mothers are going to grow buds more vigorously.
It might be that a cutting from a plant that was cloned (rather than from a seed plant) already knows how to grow roots well because the mother plant has been through the cloning process. That's the only reason I can see for using a clone for a mother but I would always try and pick the most vigorous, healthiest one, I wouldn't pick one with less vigor to save space and money.
Hope that helps