Do you prefer single-tasking or multi-tasking? Why?

Either or is fine. However the higher one climbs up the ladder the need to develop a multi tasking approach is vital to success. 

From a personal level I prefer multi tasking as it allows for a broader view of concept, especially when I encounter a mental block. I am able to leave one aspect and return later with a different approach

Single or multi tasking will depend on the ability & understanding to complete a given task. Single tasking can be done without any confusion while sometimes multi tasking can create confusion.

Hi The ability and willingness of the employee and his experience in the fields granted determine his ability to carry one or several tasks at one stage

I prefer multi-tasking because it makes me more reliable, and independent. Being a multi-tasker you also have several choices to make related to your field of interest, but on the other hand, single-tasker is bounded with very few or no choices to make and for growth purposes.

It is just like that you know how to drive a two-wheeler but doesn't know how to drive a four-wheeler.