>>1434466The Merida will be the most aggressive bike if the 73* HTA and low tire clearance (looks like it comes with 23mm wide tires stock) is anything to judge by, so it won't be very comfortable if you're a new rider. It looks to be an old model, too...2014?
The Domane is more laid-back, with the other two in the middle. One really nice thing about the Domane is that it has clearance for 32mm wide tires, whereas the rest only have clearance for 28 or maybe only 25 in the case of the Merida, so you can put wider tires on and improve ride quality if you have shitty roads or if you ride on dirt. I'd go with that.
>>1434476I'm not seeing disc brake mounts on the Giant tho. x8 is fine if it's newer Claris.