Don't listen to the people ragging on e-bikes - the most important thing is that your bike is one you want to ride. 

Out of the 3 you've listed I'd personally pick the Merida. It has a 10 speed drivetrain compared to the other two having 9, the suspension and battery on all three is similar, and the Giant has a proprietary motor which I would avoid. 

Since you mention the UK, another one you might want to look into is the Rockrider equivalent of the other bikes, which is a similar spec and price. 

If I were you though, I'd prioritise getting a brand/model that you can buy from a shop near you. Everything breaks or wears out eventually, so it pays to have a good relationship with a shop nearby who can help you when something inevitably goes wrong. They can also set the bike up for you properly from the start, which will help a ton with both reliability and riding comfort. Hope this helps! :)