I assume you're going to be riding over the Alps. That first bike looks like it has a compact double with a 28-tooth cassette, although the specs don't say. If you've got a lot of mountains to climb, you'd probably be better off with a triple. Maybe you're young and strong and wouldn't have any trouble on this one, but personally I would never attempt it on anything but a triple with fairly low climbing gears. And if this tour is unsupported (you're carrying your own gear), even more so. In fact if that's the case I wouldn't even consider this bike.

Another problem is knowing how it fits you. If you can't ride it before ordering it, stay away. You do not want to ride from London to Rome on a bike that does not fit you correctly. Small differences in frame size can have a big detrimental effect on your ride. Different manufacturers use different frame tube measurements, even if the seat post length is the same. Don't buy something you can't test ride first, and after you find the right frame size, consider having a knowledgeable bike shop adjust the fit to you. Either that, or read up on bike fit and do it yourself.