i am not certain but i think that H means hand-dyed and T means tumble-dyed in a machine. if there is no H or T, just assume that it is a T. the hand-dyed ones tend to have undyed lining and uniquely dyed outer leather
^^ go with the aesthetic you like buddy. These shoes are different in design. For comfort both will be good. Guids more summery, unstructured, softer vibe less aggresive. Roo also better for no socks wear - can easily do shorts with them. Or just get layer-0 now check them out if not like resell them and get guids.
Dude, pick what you like. Don't mind the quality - it's good no matter what. I had both Carpe and Guidi derbies in the past. Sold both but now have a pair of 992s coming my way from Hide-m. They sure are the more comfortable choice.