I like jankoc's describtion. But there should be also something speeding up by navigating well.
Like technicality is combination of how much faster certain runner can run in given section of terrain by optimal navigation compared to the speed he runs just straight without trying to navigate and
how much the orienteering difficulties make it necessary for the runner to slow down to orienteer compared to the running speed the runner would be able to keep without orienteering/map-reading.
Second part vary with person, but first part will not vary that much.
mnipen, I liked the 25manna terrain and event overall. I am familiar with that terrain type, we have lots of that here where I live. I just did not like the map, it was inaccurate, erroneous and confusing. No wonder people had bad races there, it may have nothing to do with technicality. Maybe explanation is needed here, below is the same map clip (upside down):
Imagine approaching from down (black line) and while running the side of the hill you plan ahead and try to figure in advance how the profile between A and B will look like when you climb to the long knoll (at end of black line). Knolls A and B are drawn with same full contour level, so they should be at same level. All form lines are going down to left and the one near knoll A is the lowest of them all, so it should be quite near to the level of the lower full contour. This all isn't possible unless knoll A is high and steep, like tower. It must be the most prominent feature there! It sure doesn't look like that at first glance of the map, so one can say it's not that well mapped. Then, if it's not that prominent, then knolls A and B most likely are not at same level at all, and that makes it even worse mapping - it means you can't trust full controls more than form lines - it means you really can't know how it looks in 3d by looking at contours, you will have to there and read controls as 2d objects instead of 3d. This usually happens when mappers start using stacked form lines. At minimum the third dimension becomes shaky, you can't know is form lines in halfway between contours at all. But almost always level inaccuracy spreads to full contours too and 3D isn't just shaky any more, it gets broken. In 25manna map most of time i didn't matter where did you looked, profiles and levels looked all wrong. So one had to read contours as 2D point features and usually it was pointless to read them in advance you had to read them saw them. That made the navigation quite annoying. This mapping style punishes skilled athletes, they just can't use their skills, they have to navigate like less skilled athletes do, mechanical reading of 2d objects instead of understanding the big picture in 3d well in advance.
So, as you said, if it is there map it. Altitudes, levels, all that 3d surface is there, it's the most prominent feature out there. I'd like to see it mapped instead of obsolete point feature style 2D reentrants. Mapping "everything" with stacks of form lines leads to lots of countours but less information, worse legibility, requests of larger map scale / using loops and so on.