You seem drawn to the road bikes rather than the hybrids. That's fine but I would suggest riding both a road bike and a hybrid to make sure that's what you want. The Scott is a far better bike than the Denali and well worth the extra cost.

The Denali in that posting has an odd mix of parts. It looks like the rear shifter is an STI while the front derailleur is controlled by the stem shifter. It's just weird. The replacement parts are better than stock but that STI shifter looks like it's had a few rough miles put on it. My personal opinion is that Denalis are so cheap that there isn't much reason to buy a used one.

Just one caution about the Bianchi. 650c is a less common wheel size. It's not that big of deal, it's just that bike shops may not always have a huge selection of tires. If you really like it, I wouldn't let that stop you from buying it, just know that going in.