Kelstar. there really isn't a real choice the flat top carbs are not worth rebuilding. The by far preferred carb is the SU or round top unit . before you get into them save some time and get the video from Z-therpy it's a must if you really want to know what what. I have never heard of "skinners" Gary Portland Or
I think he is referring to the fact that the SU name was from the original name "Skinners Union". They are all SU carbs, licensed to be built by Hitachi. (Both round and flattops). The later flattops just were not as good a design as the roundtops, or as simple to work on. They were a stopgap emissions carb that were only used for 2 years, 73-74 (in the US). Use the dome topped carbs, and save the flattops for paperweights, or doorstops.