Well if you can't decide, why not get both?... Just make sure that when you are mixing breads, that you order them from the same breeder,or else health problems might arise.
If you just want to do one, here are some helpers:
As far as color goes, Kuda are more likely to have a bright yellow or white coloration than Erectus who tend to stick with earth tones like purple, dark red, brown and occasionally will take on bright yellow, and orange colors.
If you are looking to raise the fry eventually, definitely go with Erectus as they hitch right from birth, and can eat baby brine shrimp as soon as they are born (no need for rotifers)