I've tried both and much prefer using Tracklogs. IMO the user interface is much more consistent and intuitive, mainly because it adhears reasonably well to current Windows interface conventions. Memorymap feels more 'homemade'.
For me, Tracklog's licensing was cheaper for the areas I needed. As far as I'm aware, only Memorymap includes maps from outside the UK.
Both have a similar 3D capability, although this is much more a toy than anything else; the real hill pain info comes from the 'Profile' graph and 'Statistics' table.
One thing you might notice about the terrain info is that it will tend to smooth out the worst of the inclines. For the lumpy stuff around Winchester, I reckon that a hill that tracklogs estimates has a maximum gradient of 8% will have at least a few metres of 12% or more (i.e. a factor of 1.5). Its only a rule of thumb, but it seems to work and my knees like to be pre-warned.
Although you can get hold of very high resolution elevation data these days from LIDAR or laser-rangefinder surveys, its likely that this has been subsampled for Tracklogs (and almost definitely Memorymap too) to give a manageable data set size. This will act like a low-pass filter and lose the short-sharp incline detail.

God, I'm boring!