over the top, it's easier I think, though somtimes I go under, depends whether I'm working directly out of the back doors of the van, or out of the side door on the van.
Winding it in is easier over the top, it is easier to guide the hose from side to side that way and if you have the good quality steel hose reels you can wind in 100m of normal tricoflex very quickly indeed (even easier with microbore no doubt).
Ian