I would think a Mystery 10 would "always" have a better selection than a Mystery 5, but that doesn't seem to be the case at all.
Generally, when I'm filling orders for Mystery Boxes, the greater number of plants in the Mystery Box usually means a greater quantity of each indivual included clone, not a greater variety of clones. Even in a 20-plant Mystery Box, if shipped by me (Steve) here in New Mexico, there is likely to be only 2-5 distinct clones or plants.
In a 20-plant Mystery Box, each plant costs less than $1.50. To me, even if all 20 plants were the same clone, that's a great price for the plants. Even the 5-plant Mystery Box plants are cheap at about $2.00 per plant. The plants are often a little on the small side, but they are healthy (despite a possible blackened trap or two) and with good care can grow into mature adults as impressive as any of the more expensive plants sold at FlytrapStore.com.
I understand why some people would be disappointed, but the Mystery Box is a gamble. Sometimes the gamble pays off, and sometimes perhaps it doesn't in the mind of the recipient. That's the nature of the product and why it's so cheap. So a person may complain about the plants, but they certainly can't complain (in my opinion) about the price.