Imust admit that for operations I prefer retractable undercarriage but we also carry a crewman at all times. For training though I have to go for skids with a low belly. This increases the "1 foot bubble". the upshot of this is to make landing much more difficult for a student. They tend to slide of the bubble and overcontrol but when they do get it right you know that they can actually land a helicopter and not just plonk it on the oleos from 2-3 feet.
