"Technology" may trickle down, but not entirely. The tucked-in Shadow parallelogram has been moving down-market. Deore is still the lowest level with a clutch and all the clutch models are 10+ speeds.
Quality does not trickle down. The levels are sliced pretty thin but...
XT will get you mostly ano aluminum forgings, any steel parts plated or stainless
Deore will get you a mostly-metal assembly with powder coat or some other really tough paint on the some of the steel, some parts stainless, and a few aluminum forgings
Tourney is all galvanized stamped steel and injection molded plastic
__________________
Genesis 49:16-17