aloha, i would collect pollen from the dwarf if it had short internodal distance
it could be a possibility that the plant is short due to loss of hybrid vigor, which means reinfusing new genetics would provide a higher vigor when the genes recombinate
does the stem feel hollow or pulpy? dj short says to choose males with empty stems, as if they are creating a lot of fiber, thats probably all they are good for
i choose males based on many factors, but ultimately if you are following a breeding program you are going to have to go with the traits you want and destroy any unwanted genetics
some of the factors I initially select males are is
-vigor
-internodal distance
-resistance to pests and diseases
-scent/aroma when the stem is rubbed
-leaf type and structure
-boquet structure
-flowering time(usually males who show sex later are better)
-hermaphrodites(i would only use reverse hermaphrodite males, which means a male which grows female pistils, this means you will have a population which is more prone to be female, IMNSHO to use any other hermaphrodites in breeding is asking for trouble. im not a fan of feminized seeds as you will have hermies if conditions are not optimal, however sometimes hermies are needed to save genetics)
if you are trying to make a strains with true-breeding traits it gets even more difficult, as you will have to choose all these factors then get rid of any in your population with unwanted genes or do not show the phenotype you want
its actually much more difficult to select males as opposed to females, males are less obvious in their talents and most of the time you have to use multiple males seeding cloned mothers, and grow out the progeny, a hefty task indeed, especially if you can only grow out 7 plants at a time, which is the main difficulty closet growers have in their breeding attempts.
population size. sometimes phenotypes and traits dont show up in populations til you grow out 50-100 plants, seeing how we can only grow a limited number of plants i would ultimately choose males on the basis of structure and health.
sorry if this was a long and boring read but i love talking about growing