Hello Gareth,
Answers on a first try in adaptive mode and answers in deferred feedback mode shouldn't differ much, in principle, since it's a first try and a single try, which is about the same.
Obviously, answers on the last try in adaptive mode should normally be better than on the first try or in deferred feedback mode.
In general, the adaptive mode would be more appropriate for formative assessments, while the deferred feedback mode would be more appropriate for summative assessments.
Personally, I use the adaptive mode even for summative assessments because I consider that it is of little use for students to be blocked without having any clues, and without having one or more attempts to answer questions. Indeed, in my view, the primary purpose of quizzes, both formative and summative, is for students to learn about a topic.
The summative aspect is well taken into account in adaptive mode thanks to the penalties for each try. Better students get more points for answering questions correctly on the first try, while weaker students lose points for answering correctly only on the second or more tries, or for not getting the correct answer even after the number of tries allowed.
So, unless I want to do a very strict summative evaluation, which I don't necessarily see the benefit for the students, I don't use the deferred feedback mode. There are obviously a multitude of cases other than mine where the deferred feedback mode is useful.