Here is the low down on the bikes your asking about. The Scale is a lightweight race bike with race geometry. The scale is nice for racing and short distances, but probably not what you want for a long ride. The epic is also a race bike, but unlike the scale it is dual suspension and will be much more comfortable over those long miles.
The scott genius is a trail bike that will be comfortable to ride all day due to it 5 inches of travel on the fornt and rear. The cool think about the genius is that you can dial down the suspension to as low as 3 inches if you wanted to race it. The serious racer probably will not buy a genius, but a casual racer that wants a bike that can handle just about anything and still be light, will love the genius.
Now, I thought I would mention that I have a fairly good amount of mileage on all three of these bikes and as you can tell the genius is my favorite.