I have no study to cite at this stage, but I can offer some of my experience of working with thousands of students in my Maths Learning Centre.
In my experience, students dislike things that are difficult to follow and difficult to find information in by themselves. They like things with clear layout and organisation, with important information highlighted and summarised, and where different parts of the text (proofs, examples, worked examples) are clearly delineated. These are not just likes and dislikes either, but I have seen a change in the structure of the notes encourage more independent learning between two semesters of the same course.
In terms of being able to achieve this organisation, the good things can be achieved in both handwritten and typed materials, and badly-organised things can exist in both. Personally I have found that you have to work harder with handwritten materials to be organised, especially if you are making them up on the fly. LaTeX has a natural structure of chapter-section-subsection-etc which helps you to be more organised as you type.
Already-written maths notation
In the specific case of worked examples of problem-solving, my experience is that maths that is already written down does not make any sense. The eye naturally slips over equations and symbols, often not pausing to even recognise the names of the symbols. Moreover, if you are projecting maths onto a screen in your lecture, the students will never have enough time to read it and understand what is going on, no matter how slow you think you're taking it. Already-written symbols are just too difficult to parse at any speed.
Leading by example
Finally, I believe that the goal of a worked example is to show what students are supposed to do themselves, and so worked examples should look as close as possible to what you expect the students to do. It is easier to imagine doing the maths yourself if it is handwritten. Moreover, you are more able to imagine how long it takes them to do it and the difficulties they face if you are doing yourself what you have asked them to do!
You could apply this argument to the information text as well. If you want them to learn the skill of reading maths (such as proofs etc), then you probably want to present those parts in the format they are likely to see in textbooks, journal articles etc -- that is, it might be better to have this part typed. [A caveat is that since maths that is already written down doesn't make sense, if I were presenting a proof in class, I would handwrite it even though it was typed in the notes. Alternatively, I would take the typed version and mark it up with highlighting and extra working just like I would if I was reading a real journal article myself.]
In light of my experience, I would recommend typing most of the materials you give to students, but handwriting anything that is supposed to show them how to do something for themselves.