Having a retractable cord necessitates having a box inside your TT which takes up valuable space (every cubic inch of storage is like gold in a TT). I installed a detachable cord on our 1st TT and gained some extra storage space which was quite helpful. Just required a removable lid and was accessible from the outside.
A retractable cord can get tangled inside the box. A detachable cord eliminates this. A retractable cord in cold weather is a PITA to work with. A detachable cord is faster to set up and not a problem in cold weather.
Having a detachable cord could potentially lead to a meltdown if you don't routinely shut the power off first.
A detachable cord fits easily into a pass-through compartment. Sometimes I just toss it in the back of the truck because it gets used at home or the next CG anyway.
I much prefer having a detachable cord.