I have never ridden any of the bikes on the list, but fwiw from the specs I would say the Raleigh and the Sedona have front suspension so will likely be around 1.5 kgs heavier than the others. Since you have an mtb already, I presume you are not really after another bike with front suspension.
The other 3 are not very different, but if I had to choose just based on spec I would choose the
Ridgeback. It has decent tyres and components that are a little better than the others. I would expect it to be one of the lightest and quickest for road use on the list. However buying online just based on spec without trying it out for fit and feel is risky - it won't be much good to you if the size/geometry doesn't fit you well.
Of course the other possibility is to upgrade your existing Giant mtb. You did not say which model it is or what is wrong with it, but assuming it is in good repair there are a few things you could potentially do to make it nearly if not exactly as efficient as the Ridgeback. Firstly rolling resistance is mainly about tyres - switching big mtb knobblies to a pair of 1.5", light, high pressure slicks (such as the Continental Sport Contact) pumped up to maximum design pressure (probably 80 psi or so) will make a noticeable difference, also if the bike has suspension either lock it out or maximise preload if possible may also help. Finally most people ride their bikes with the saddle set too low, getting it up to the
right height will make a massive difference to effort required.
Welcome to the forum, and good luck!
