Hi John
All three are great bikes! The main difference between the Agattu, Monark and E-Motion is that the Agattu and Monark have internal hub gears and the E-Motion has derailleur gears.
There are arguments for and against both systems, with internal hubs being easier to maintain and derailleurs being more efficient.
With internal hub gears you can change gear without pedaling, whereas with a derailleur you do not have to take the power off when changing gear, especially useful when going uphill - It's a personal choice.
Top of the range bikes normally have derailleur systems, like the Kalkhoff Pro Connect S and the Flyer S series Cross.
The other main differences are the lights come from a dynamo on the Agattu and Monark, whereas they come from the main battery on the E-Motion and more expensive Kalkhoffs. This saves weight and improves rolling resistance especially when the lights are on. In the absence of a dynamo and hub gears you can also have quick release wheels, which allows quicker puncture repair and removal of wheels for loading into a car.
Before someone points out that the wheels can be stolen more easily, I should say you can get locking quick release skewers!
The E-Motion also has a quick release handlebar adjust, which allows for different riding positions depending on what style of riding you are doing that day.
You can change the rear cassette on the E-Motion, which is currently 14-28 tooth. If you changed the cassette you could have 11-32 or 11-30 tooth casette that would give you assistance up to about 18MPH! Although this would not be road legal. If you choose a 32 tooth sproket the hill climbing ability is amazing! Any good cycling shop can change a casette normally charging around £25.
Don't wait another three months to decide. Tour de Presteigne is only two weeks away, so come along and try all three bikes side by side. I always believe the best bike is the one you are most comfortable on.
Hope this helps
Andy